MySQL Reference Manual for version 3.22.27.

1 General Information about MySQL

This is the MySQL reference manual; it documents MySQL version 3.22.27.

MySQL is a very fast, multi-threaded, multi-user and robust SQL (Structured Query Language) database server.

For Unix and OS/2 platforms, MySQL is basically free; for Microsoft platforms you must get a MySQL license after a trial time of 30 days. See section 3 MySQL licensing and support.

The MySQL home page provides the latest information about MySQL.

For a discussion of MySQL's capabilities, see section 1.4 The main features of MySQL.

For installation instructions, see section 4 Installing MySQL. For tips on porting MySQL to new machines or operating systems, see section G Comments on porting to other systems.

For information about upgrading from a 3.21 release, see section 4.16.2 Upgrading from a 3.21 version to 3.22.

For a tutorial introduction to MySQL, see section 8 MySQL Tutorial.

For examples of SQL and benchmarking information, see the benchmarking directory. For source distributions, this is the `bench' directory. For binary distributions, this is the `sql-bench' directory.

For a history of new features and bug fixes, see section D MySQL change history.

For a list of currently known bugs and misfeatures, see section E Known errors and design deficiencies in MySQL.

For future plans, see section F List of things we want to add to MySQL in the future (The TODO).

For a list of all the contributors to this product, see section C Contributors to MySQL.

IMPORTANT:

Send bug (error) reports, questions and comments to the mailing list at

For source distributions, the mysqlbug script can be found in the `scripts' directory. For binary distributions, mysqlbug can be found in the `bin' directory.

If you have any suggestions concerning additions or corrections to this manual, please send them to the MySQL mailing list (mysql@lists.mysql.com) with the following subject line: documentation suggestion: [Insert Topic Here]. See section 2.1 The MySQL mailing lists.

1.1 What is MySQL?

MySQL is a true multi-user, multi-threaded SQL database server. SQL is the most popular database language in the world. MySQL is a client/server implementation that consists of a server daemon mysqld and many different client programs and libraries.

SQL is a standardized language that makes it easy to store, update and access information. For example, you can use SQL to retrieve product information and store customer information for a web site. MySQL is also fast and flexible enough to allow you to store logs and pictures in it.

The main goals of MySQL are speed, robustness and ease of use. MySQL was originally developed because we at TcX needed a SQL server that could handle very large databases an order of magnitude faster than what any database vendor could offer to us. We have now been using MySQL since 1996 in an environment with more than 40 databases containing 10,000 tables, of which more than 500 have more than 7 million rows. This is about 100 gigabytes of mission-critical data.

The base upon which MySQL is built is a set of routines that have been used in a highly demanding production environment for many years. Although MySQL is still under development, it already offers a rich and highly useful function set.

The official way to pronounce MySQL is "My Ess Que Ell" (Not MY-SEQUEL).

1.2 About this manual

This manual is currently available in Texinfo, plain text, Info, HTML, PostScript and PDF versions. Because of their size, PostScript and PDF versions are not included with the main MySQL distribution, but are available for separate download at http://www.mysql.com.

The primary document is the Texinfo file. The HTML version is produced automatically with a modified version of texi2html. The plain text and Info versions are produced with makeinfo. The Postscript version is produced using texi2dvi and dvips. The PDF version is produced with the Ghostscript utility ps2pdf.

This manual is written and maintained by David Axmark, Michael (Monty) Widenius, Paul DuBois and Kim Aldale. For other contributors, see section C Contributors to MySQL.

1.2.1 Conventions used in this manual

This manual uses certain typographical conventions:

constant

Constant-width font is used for command names and options; SQL statements; database, table and column names; C and Perl code; and environment variables. Example: "To see how mysqladmin works, invoke it with the --help option."

`filename'

Constant-width font with surrounding quotes is used for filenames and pathnames. Example: "The distribution is installed under the `/usr/local/' directory."

`c'

Constant-width font with surrounding quotes is also used to indicate character sequences. Example: "To specify a wildcard, use the `%' character."

italic

Italic font is used for emphasis, like this.

boldface

Boldface font is used for access privilege names (e.g., "do not grant the process privilege lightly") and to convey especially strong emphasis.

When commands are shown that are meant to be executed by a particular program, the program is indicated by the prompt shown with the command. For example, shell> indicates a command that you execute from your login shell, and mysql> indicates a command that you execute from the mysql client:

shell> type a shell command here
mysql> type a mysql command here

Shell commands are shown using Bourne shell syntax. If you are using a csh-style shell, you may need to issue commands slightly differently. For example, the sequence to set an environment variable and run a command looks like this in Bourne shell syntax:

shell> VARNAME=value some_command

For csh, you would execute the sequence like this:

shell> setenv VARNAME value
shell> some_command

Database, table and column names often must be substituted into commands. To indicate that such substitution is necessary, this manual uses db_name, tbl_name and col_name. For example, you might see a statement like this:

mysql> SELECT col_name FROM db_name.tbl_name;

This means that if you were to enter a similar statement, you would supply your own database, table and column names, perhaps like this:

mysql> SELECT author_name FROM biblio_db.author_list;

SQL statements may be written in uppercase or lowercase. When this manual shows a SQL statement, uppercase is used for particular keywords if those keywords are under discussion (to emphasize them) and lowercase is used for the rest of the statement. So you might see the following in a discussion of the SELECT statement:

mysql> SELECT count(*) FROM tbl_name;

On the other hand, in a discussion of the COUNT() function, the statement would be written like this:

mysql> select COUNT(*) from tbl_name;

If no particular emphasis is intended, all keywords are written uniformly in uppercase.

In syntax descriptions, square brackets (`[' and `]') are used to indicate optional words or clauses:

DROP TABLE [IF EXISTS] tbl_name

When a syntax element consists of a number of alternatives, the alternatives are separated by vertical bars (`|'). When one member from a set of choices may be chosen, the alternatives are listed within square brackets. When one member from a set of choices must be chosen, the alternatives are listed within braces (`{' and `}'):

TRIM([[BOTH | LEADING | TRAILING] [remstr] FROM] str)
{DESCRIBE | DESC} tbl_name {col_name | wild}

1.3 History of MySQL

We once started off with the intention of using mSQL to connect to our tables using our own fast low-level (ISAM) routines. However, after some testing we came to the conclusion that mSQL was not fast enough or flexible enough for our needs. This resulted in a new SQL interface to our database but with almost the same API interface as mSQL. This API was chosen to ease porting of third-party code.

The derivation of the name MySQL is not perfectly clear. Our base directory and a large number of our libraries and tools have had the prefix "my" for well over 10 years. However, Monty's daughter (some years younger) is also named My. So which of the two gave its name to MySQL is still a mystery, even for us.

1.4 The main features of MySQL

The following list describes some of the important characteristics of MySQL:

• Fully multi-threaded using kernel threads. That means it easily can use multiple CPUs if available.
• C, C++, Eiffel, Java, Perl, PHP, Python and TCL APIs. See section 20 MySQL client tools and APIs.
• Works on many different platforms. See section 4.2 Operating systems supported by MySQL.
• Many column types: signed/unsigned integers 1, 2, 3, 4 and 8 bytes long, FLOAT, DOUBLE, CHAR, VARCHAR, TEXT, BLOB, DATE, TIME, DATETIME, TIMESTAMP, YEAR, SET and ENUM types. See section 7.2 Column types.
• Very fast joins using an optimized one-sweep multi-join.
• Full operator and function support in the SELECT and WHERE parts of queries. Example:

  mysql> SELECT CONCAT(first_name, " ", last_name) FROM tbl_name
             WHERE income/dependents > 10000 AND age > 30;
  

• SQL functions are implemented through a highly-optimized class library and should be as fast as they can get! Usually there shouldn't be any memory allocation at all after query initialization.
• Full support for SQL GROUP BY and ORDER BY clauses. Support for group functions (COUNT(), COUNT(DISTINCT), AVG(), STD(), SUM(), MAX() and MIN()).
• Support for LEFT OUTER JOIN with ANSI SQL and ODBC syntax.
• You can mix tables from different databases in the same query (as of version 3.22).
• A privilege and password system which is very flexible and secure, and which allows host-based verification. Passwords are secure since all password traffic when connecting to a server is encrypted.
• ODBC (Open-DataBase-Connectivity) for Windows95 (with source). All ODBC 2.5 functions and many others. You can, for example, use Access to connect to your MySQL server. See section 16 MySQL ODBC Support.
• Very fast B-tree disk tables with index compression.
• 16 indexes per table are allowed. Each index may consist of 1 to 16 columns or parts of columns. The maximum index length is 256 bytes (this may be changed when compiling MySQL). An index may use a prefix of a CHAR or VARCHAR field.
• Fixed-length and variable-length records.
• In-memory hash tables which are used as temporary tables.
• Handles large databases. We are using MySQL with some databases that contain 50,000,000 records.
• All columns have default values. You can use INSERT to insert a subset of a table's columns; those columns that are not explicitly given values are set to their default values.
• Uses GNU Automake, Autoconf, and libtool for portability.
• Written in C and C++. Tested with a broad range of different compilers.
• A very fast thread-based memory allocation system.
• No memory leaks. Tested with a commercial memory leakage detector (purify).
• Includes isamchk, a very fast utility for table checking, optimization and repair. See section 13 Maintaining a MySQL installation.
• Full support for the ISO-8859-1 Latin1 character set. For example, the Scandinavian characters @ringaccent{a}, @"a and @"o are allowed in table and column names.
• All data are saved in ISO-8859-1 Latin1 format. All comparisons for normal string columns are case insensitive.
• Sorting is done according to the ISO-8859-1 Latin1 character set (the Swedish way at the moment). It is possible to change this in the source by adding new sort order arrays. To see an example of very advanced sorting, look at the Czech sorting code. MySQL supports many different character sets that can be specified at compile time.
• Aliases on tables and columns as in the SQL92 standard.
• DELETE, INSERT, REPLACE, and UPDATE return how many rows were changed (affected).
• Function names do not clash with table or column names. For example, ABS is a valid column name. The only restriction is that for a function call, no spaces are allowed between the function name and the `(' that follows it. See section 7.30 Is MySQL picky about reserved words?.
• All MySQL programs can be invoked with the --help or -? options to obtain online assistance.
• The server can provide error messages to clients in many languages. See section 9.1 What languages are supported by MySQL?.
• Clients connect to the MySQL server using TCP/IP connections or Unix sockets, or named pipes under NT.
• The MySQL-specific SHOW command can be used to retrieve information about databases, tables and indexes. The EXPLAIN command can be used to determine how the optimizer resolves a query.

1.5 How stable is MySQL?

This section addresses the questions, "how stable is MySQL?" and, "can I depend on MySQL in this project?" Here we will try to clarify some issues and to answer some of the more important questions that seem to concern many people. This section has been put together from information gathered from the mailing list (which is very active in reporting bugs).

At TcX, MySQL has worked without any problems in our projects since mid-1996. When MySQL was released to a wider public, we noticed that there were some pieces of "untested code" that were quickly found by the new users who made queries in a manner different than our own. Each new release has had fewer portability problems than the previous one (even though each has had many new features), and we hope that it will be possible to label one of the next releases "stable".

Each release of MySQL has been usable and there have been problems only when users start to use code from "the gray zones". Naturally, outside users can't know what the gray zones are; this section attempts to indicate those that are currently known. The descriptions deal with the 3.22.x version of MySQL. All known and reported bugs are fixed in the latest version, with the exception of the bugs listed in the bugs section, which are things that are "design"-related. See section E Known errors and design deficiencies in MySQL.

MySQL is written in multiple layers and different independent modules. These modules are listed below with an indication of how well-tested each of them is:

The ISAM table handler -- Stable

This manages storage and retrieval of all data in MySQL 3.22 and earlier versions. In all MySQL releases there hasn't been a single (reported) bug in this code. The only known way to get a corrupted table is to kill the server in the middle of an update. Even that is unlikely to destroy any data beyond rescue, because all data are flushed to disk between each query. There hasn't been a single bug report about lost data because of bugs in MySQL, either.

The MyISAM table handler -- Beta

This is new in MySQL 3.23. It's largely based on the ISAM table code but has a lot of new very useful features.

The parser and lexical analyser -- Stable

There hasn't been a single reported bug in this system for a long time.

The C client code -- Stable

No known problems. In early 3.20 releases, there were some limitations in the send/receive buffer size. As of 3.21.x, the buffer size is now dynamic up to a default of 24M.

Standard client programs -- Stable

These include mysql, mysqladmin and mysqlshow, mysqldump, and mysqlimport.

Basic SQL -- Stable

The basic SQL function system and string classes and dynamic memory handling. Not a single reported bug in this system.

Query optimizer -- Stable

Range optimizer -- Gamma

Join optimizer -- Stable

Locking -- Gamma

This is very system-dependent. On some systems there are big problems using standard OS locking (fcntl()). In these cases, you should run the MySQL daemon with the --skip-locking flag. Problems are known to occur on some Linux systems and on SunOS when using NFS-mounted file systems.

Linux threads -- Gamma

The only problem found has been with the fcntl() call, which is fixed by using the --skip-locking option to mysqld. Some people have reported lockup problems with the 0.5 release.

Solaris 2.5+ pthreads -- Stable

We use this for all our production work.

MIT-pthreads (Other systems) -- Gamma

There have been no reported bugs since 3.20.15 and no known bugs since 3.20.16. On some systems, there is a "misfeature" where some operations are quite slow (a 1/20 second sleep is done between each query). Of course, MIT-pthreads may slow down everything a bit, but index-based SELECT statements are usually done in one time frame so there shouldn't be a mutex locking/thread juggling.

Other thread implementions -- Alpha - Beta

The ports to other systems are still very new and may have bugs, possibly in MySQL, but most often in the thread implementation itself.

LOAD DATA ..., INSERT ... SELECT -- Stable

Some people have thought they have found bugs here, but these usually have turned out to be misunderstandings. Please check the manual before reporting problems!

ALTER TABLE -- Stable

Small changes in 3.22.12.

DBD -- Stable

Now maintained by Jochen Wiedmann

mysqlaccess -- Stable

Written and maintained by Yves Carlier

GRANT -- Gamma

Big changes made in MySQL 3.22.12.

MyODBC (uses ODBC SDK 2.5) -- Beta

It seems to work well with some programs.

TcX provides email support for paying customers, but the MySQL mailing list usually provides answers to common questions. Bugs are usually fixed right away with a patch; for serious bugs, there is almost always a new release.

1.6 Year 2000 compliance

MySQL itself has no problems with Year 2000 (Y2K) compliance:

• MySQL uses Unix time functions and has no problems with dates until 2069; all 2-digit years are regarded to be in the range 1970 to 2069, which means that if you store 01 in a year column, MySQL treats it as 2001.
• All MySQL date functions are stored in one file `sql/time.cc' and coded very carefully to be year 2000-safe.
• In MySQL 3.22 and later versions, the new YEAR column type can store years 0 and 1901 to 2155 in 1 byte and display them using 2 or 4 digits.

You may run into problems with applications that use MySQL in a way that is not Y2K-safe. For example, many old applications store or manipulate years using 2-digit values (which are ambiguous) rather than 4-digit values. This problem may be compounded by applications that use values such as 00 or 99 as "missing" value indicators.

Unfortunately, these problems may be difficult to fix, since different applications may be written by different programmers, each of whom may use a different set of conventions and date-handling functions.

Here is a simple demonstration illustrating that MySQL doesn't have any problems with dates until the year 2030!

mysql> DROP TABLE IF EXISTS y2k;
mysql> CREATE TABLE y2k (date date, date_time datetime, time_stamp timestamp);
mysql> INSERT INTO y2k VALUES ("1998-12-31","1998-12-31 23:59:59",19981231235959);
mysql> INSERT INTO y2k VALUES ("1999-01-01","1999-01-01 00:00:00",19990101000000);
mysql> INSERT INTO y2k VALUES ("1999-09-09","1999-09-09 23:59:59",19990909235959);
mysql> INSERT INTO y2k VALUES ("2000-01-01","2000-01-01 00:00:00",20000101000000);
mysql> INSERT INTO y2k VALUES ("2000-02-28","2000-02-28 00:00:00",20000228000000);
mysql> INSERT INTO y2k VALUES ("2000-02-29","2000-02-29 00:00:00",20000229000000);
mysql> INSERT INTO y2k VALUES ("2000-03-01","2000-03-01 00:00:00",20000301000000);
mysql> INSERT INTO y2k VALUES ("2000-12-31","2000-12-31 23:59:59",20001231235959);
mysql> INSERT INTO y2k VALUES ("2001-01-01","2001-01-01 00:00:00",20010101000000);
mysql> INSERT INTO y2k VALUES ("2004-12-31","2004-12-31 23:59:59",20041231235959);
mysql> INSERT INTO y2k VALUES ("2005-01-01","2005-01-01 00:00:00",20050101000000);
mysql> INSERT INTO y2k VALUES ("2030-01-01","2030-01-01 00:00:00",20300101000000);
mysql> INSERT INTO y2k VALUES ("2050-01-01","2050-01-01 00:00:00",20500101000000);
mysql> SELECT * FROM y2k;
+------------+---------------------+----------------+
| date       | date_time           | time_stamp     |
+------------+---------------------+----------------+
| 1998-12-31 | 1998-12-31 23:59:59 | 19981231235959 |
| 1999-01-01 | 1999-01-01 00:00:00 | 19990101000000 |
| 1999-09-09 | 1999-09-09 23:59:59 | 19990909235959 |
| 2000-01-01 | 2000-01-01 00:00:00 | 20000101000000 |
| 2000-02-28 | 2000-02-28 00:00:00 | 20000228000000 |
| 2000-02-29 | 2000-02-29 00:00:00 | 20000229000000 |
| 2000-03-01 | 2000-03-01 00:00:00 | 20000301000000 |
| 2000-12-31 | 2000-12-31 23:59:59 | 20001231235959 |
| 2001-01-01 | 2001-01-01 00:00:00 | 20010101000000 |
| 2004-12-31 | 2004-12-31 23:59:59 | 20041231235959 |
| 2005-01-01 | 2005-01-01 00:00:00 | 20050101000000 |
| 2030-01-01 | 2030-01-01 00:00:00 | 20300101000000 |
| 2050-01-01 | 2050-01-01 00:00:00 | 00000000000000 |
+------------+---------------------+----------------+

13 rows in set (0.00 sec)

This shows that the DATE and DATETIME types are will not give any problems with future dates (they handle dates until the year 9999).

The TIMESTAMP type, that is used to store the current time, has a range up to only 2030-01-01. TIMESTAMP has a range of 1970 to 2030 on 32-bit machines (signed value). On 64-bit machines it handles times up to 2106 (unsigned value).

Even though MySQL is Y2K-compliant, it is your responsibility to provide unambiguous input. See section 7.2.6.1 Y2K issues and date types for MySQL's rules for dealing with ambiguous date input data (data containing 2-digit year values).

1.7 General SQL information and tutorials

This book has been recommended by a several people on the MySQL mailing list:

Judith S. Bowman, Sandra L. Emerson and Marcy Darnovsky
The Practical SQL Handbook: Using Structured Query Language
Second Edition
Addison-Wesley
ISBN 0-201-62623-3
http://www.awl.com

This book has also received some recommendations on the mailing list:

Martin Gruber
Understanding SQL
ISBN 0-89588-644-8
Publisher Sybex 510 523 8233
Alameda, CA USA

A SQL tutorial is available on the net at http://www.geocities.com/SiliconValley/Vista/2207/sql1.html

SQL in 21 Tagen (online book in German language): http://www.mut.de/leseecke/buecher/sql/inhalt.htm

1.8 Useful MySQL-related links

1.8.1 Commercial applications that support MySQL

• SupportWizard; Interactive helpdesk on the web (This product includes a licensed copy of MySQL)
• Right Now Web; Web automation for customer service
• Bazaar; Interactive Discussion Forums with web interface
• PhoneSweepT is the world's first commercial Telephone Scanner. Many break-ins in recent years have come not through the Internet, but through unauthorized dial-up modems. PhoneSweep lets you find these modems by repeatedly placing phone calls to every phone number that your organization controls. PhoneSweep has a built-in expert system that can recognize more than 250 different kinds of remote-access programs, including Carbon CopyT, pcANYWHERET, and Windows NT RAS. All information is stored in the SQL database. It then generates a comprehensive report detailing which services were discovered on which dial-up numbers in your organization.

1.8.2 SQL Clients

• MySQL Editor/Utility for MS Windows Platforms.
• KDE MySQL client
• Kiosk; a MySQL client for database management. Written in Perl. Will be a part of Bazaar.

1.8.3 Web development tools that support MySQL

• PHP: A server-side HTML-embedded scripting language
• The Midgard Application Server; a powerful Web development environment based on MySQL and PHP
• SmartWorker is a platform for web application development
• XSP: e(X)tendible (s)erver (p)ages and is a HTML embedded tag language written in Java (previously known as XTAGS)
• dbServ is an extension to a web server to integrate databases output into your HTML code. You may use any HTML function in your output. Only the client will stop you. It works as standalone server or as JAVA servlet.
• Platform independent ASP from Chili!Soft
• MySQL + PHP demos
• ForwardSQL: HTML interface to manipulate MySQL databases
• WWW-SQL: Display database information
• Minivend: A Web shopping cart
• HeiTML: A server-side extension of HTML and a 4GL language at the same time
• Metahtml: A Dynamic Programming Language for WWW Applications
• VelocityGen for Perl and TCL
• Hawkeye Internet Server Suite
• Network Database Connection For Linux
• WDBI: Web browser as a universal front end to databases which supports MySQL well.
• WebGroove Script: HTML compiler and server-side scripting language
• A server-side web site scripting language
• How to use MySQL with Coldfusion on Solaris
• Calistra's ODBC MySQL Administrator
• Webmerger This CGI tool interprets files and generates dynamic output based on a set of simple tags. Ready-to-run drivers for MySQL and PostgreSQL through ODBC.
• PHPclub. Tips and tricks for PHP
• MySQL and Perl Scripts
• The Widgetchuck; Web Site Tools and Gadgets
• AdCycle advertising management software

1.8.4 Databse design tools with MySQL support

• "Dezign for databases" is a database development tool using an rick> entity relationship diagram (ERD).

1.8.5 Web servers with MySQL tools

• An Apache authentication module
• The Roxen Challenger Web server

1.8.6 Extensions for other programs

A Delphi interface to MySQL. With source code. By Matthias Fichtner.
• TmySQL; A library to use MySQL with Delphi
• Delphi TDataset-component
• Support for BIND (The Internet Domain Name Server)
• Sendmail extensions using MySQL

1.8.7 ODBC related links

• Popular iODBC Driver Manager (libiodbc) now available in Open Source format
• The FreeODBC Pages

1.8.8 API related links

• www.jppp.com Partially implemented TDataset-compatible components for MySQL.
• qpopmysql A patch to allow POP3 authentication from a MySQL database. There's also a link to Paul Khavkine's patch for Procmail to allow any MTA to deliver to users in a MySQL database.
• Visual Basic class generator for Active X
• Client libraries for the Macintosh
• MySQL binding to Free Pascal

1.8.9 Other MySQL-related links

• Registry of Web providers who support MySQL Links about using MySQL in Japan/Asia
• Commercial Web defect tracking system
• PTS: Project Tracking System
• Job and software tracking system
• ExportSQL: A script to export data from Access95+
• SAL (Scientific Applications on Linux) MySQL entry
• A consulting company which mentions MySQL in the right company
• PMP Computer Solutions. Database developers using MySQL and mSQL
• Airborne Early Warning Association
• MySQL UDF Registry
• Y2K tester

1.8.10 SQL and database interfaces

• KMySQL KMySQL is a database client for KDE that primarily supports MySQL.
• The JDBC database access API
• Patch for mSQL TCL
• EasySQL: An ODBC-like driver manager
• A REXX interface to SQL databases
• TCL interface

1.8.11 Examples of MySQL use

• Little6 Inc An online contract and job finding site that is powered by MySQL, PHP3 and Linux.
• DELECis A tool which makes it very easy to create an automatically generated table documentation. They have used MySQL as an example.
• Steve Fambro Uses MySQL and webmerger. There is an employee database, and a license plate database with all of the registered Utah vehicles (over 1.2 million). The License plate field is indexed.....so the *searches* are instantaneous.
• World Records A search engine for information about music that uses MySQL and PHP.
• Examples using MySQL; (check Top 10)
• A Contact Database using MySQL and PHP
• Web based interface and Community Calender with PHP
• Perl package to generate html from a SQL table structure and for generating SQL statements from an html form.
• Basic telephone database using DBI/DBD.
• Installing new Perl modules that require locally installed modules
• JDBC examples by Daniel K. Schneider
• SQL BNF
• Object Oriented Concepts Inc; CORBA applications with examples in source
• DBWiz; Includes an example of how to manage own cursors in VB
• Pluribus Pluribus, is a free search engine that learns to improve the quality of its results over time. Pluribus works by recording which pages a user prefers among those returned for a query. A user votes for a page by selecting it; Pluribus then uses that knowledge to improve the quality of the results when someone else submits the same (or similar) query. Uses PHP and MySQL.
• Stopbit A technology news site using MySQL and PHP
• Example scripts at Jokes2000
• MySQL-perl tutorial
• PHP/MySQL Tutorial
• FutureForum Web Discussion Software
• http://www.linuxsupportline.com/~kalendar/ KDE based calendar manager The calendar manager has both single user (file based) and multi user (MySQL database) support.
• Example of storing/retrieving images with MySQL and CGI
• Online shopping cart system
• Old Photo Album The album is a collaborative popular history of photography project that generates all pages from data stored in a MySQL database. Pages are dynamically generated through a php3 interface to the database content. Users contribute images and descriptions. Contributed images are stored on the web server to avoid storing them in the database as BLOBs. All other information is stored in on the shared MySQL server.

1.8.12 General database links

• Database Jump Site
• Homepage of the webdb-l (Web Databases) mailing list.
• Perl DBI/DBD modules homepage
• Cygwin tools (MySQL +Apache + PHP under Win32
• dbasecentral.com; Development and distribution of powerful and easy-to-use database applications and systems.
• Tek-Tips Forums Tek-Tips Forums are 800+ independent peer-to-peer non-commercial support forums for Computer Professionals. Features include automatic e-mail notification of responses, a links library, and member confidentiality guaranteed.

There are also many web pages that use MySQL. See section A Some MySQL users. Send any additions to this list to MySQL logo somewhere (It is okay to have it on a "used tools" page or something similar) to be added.

2 MySQL mailing lists and how to ask questions or report errors (bugs)

2.1 The MySQL mailing lists

To subscribe to the main MySQL mailing list, send a message to the electronic mail address mysql-subscribe@lists.mysql.com.

To unsubscribe from the main MySQL mailing list, send a message to the electronic mail address mysql-unsubscribe@lists.mysql.com.

Only the address to which you send your messages is significant. The subject line and the body of the message are ignored.

If your reply address is not valid, you can specify your address explicitly. Adding a hyphen to the subscribe or unsubscribe command word, followed by your address with the `@' character in your address replaced by a `='. For example, to subscribe john@host.domain, send a message to mysql-subscribe-john=host.domain@lists.mysql.com.

Mail to mysql-subscribe@lists.mysql.com or ezmlm mailing list processor. Information about ezmlm is available at the ezmlm Website.

To post a message to the list itself, send your message to mysql@lists.mysql.com. However, please do not send mail about subscribing or unsubscribing to mysql@lists.mysql.com, since any mail sent to that address is distributed automatically to thousands of other users.

Your local site may have many subscribers to mysql@lists.mysql.com. If so, it may have a local mailing list, so that messages sent from lists.mysql.com to your site are propagated to the local list. In such cases, please contact your system administrator to be added to or dropped from the local MySQL list.

The following MySQL mailing lists exist:

announce

This is for announcement of new versions of MySQL and related programs. This is a low volume list that we think all MySQL users should be on.

mysql

The main list for general MySQL discussion. Please note that some topics are better discussed on the more-specialized lists. If you post to the wrong list, you may not get an answer!

mysql-digest

The mysql list in digest form. That means you get all individual messages, sent as one large mail message once a day.

java

Discussion about MySQL and Java. Mostly about the JDBC drivers.

java-digest

A digest version of the java list.

win32

All things concerning MySQL on Microsoft operating systems such as Windows NT.

win32-digest

A digest version of the win32 list.

myodbc

All things concerning connecting to MySQL with ODBC.

myodbc-digest

A digest version of the myodbc list.

msql-mysql-modules

A list about the Perl support in MySQL.

msql-mysql-modules-digest

A digest version of the msql-mysql-modules list.

developer

A list for people who work on the MySQL code.

developer-digest

A digest version of the developer list.

You subscribe or unsubscribe to all lists in the same way as described above. In your subscribe or unsubscribe message, just put the appropriate mailing list name rather than mysql. For example, to subscribe to or unsubscribe from the myodbc list, send a message to

2.2 Asking questions or reporting bugs

Before posting a bug report or question, please do the following:

• Start by searching the MySQL online manual at:

  http://www.mysql.com/Manual_chapter/manual_toc.html
  

  We try to keep the manual up to date by updating it frequently with solutions to newly found problems!
• Search the MySQL mailing list archives:

  http://www.mysql.com/doc.html
  

• You can also use http://www.mysql.com/search.html to search all the web pages (including the manual) that are located at http://www.mysql.com/.

If you can't find an answer in the manual or the archives, check with your local MySQL expert. If you still can't find an answer to your question, go ahead and read the next section about how to send mail to

2.3 How to report bugs or problems

Writing a good bug report takes patience, but doing it right the first time saves time for us and for you. This section will help you write your report correctly so that you don't waste your time doing things that may not help us much or at all.

We encourage everyone to use the mysqlbug script to generate a bug report (or a report about any problem), if possible. mysqlbug can be found in the `scripts' directory in the source distribution, or, for a binary distribution, in the `bin' directory under your MySQL installation directory. If you are unable to use mysqlbug, you should still include all the necessary information listed in this section.

The mysqlbug script helps you generate a report by determining much of the following information automatically, but if something important is missing, please include it with your message! Please read this section carefully and make sure that all the information described here is included in your report.

Remember that it is possible to respond to a message containing too much information, but not to one containing too little. Often people omit facts because they think they know the cause of a problem and assume that some details don't matter. A good principle is: if you are in doubt about stating something, state it! It is a thousand times faster and less troublesome to write a couple of lines more in your report than to be forced to ask again and wait for the answer because you didn't include enough information the first time.

The most common errors are that people don't indicate the version number of the MySQL distribution they are using, or don't indicate what platform they have MySQL installed on (including the platform version number). This is highly relevant information and in 99 cases out of 100 the bug report is useless without it! Very often we get questions like "Why doesn't this work for me?" and then we find that the feature requested wasn't implemented in that MySQL version, or that a bug described in a report has been fixed already in newer MySQL versions. Sometimes the error is platform dependent; in such cases, it is next to impossible to fix anything without knowing the operating system and the version number of the platform.

Remember also to provide information about your compiler, if it is related to the problem. Often people find bugs in compilers and think the problem is MySQL related. Most compilers are under development all the time and become better version by version, too. To determine whether or not your problem depends on your compiler, we need to know what compiler is used. Note that every compiling problem should be regarded as a bug report and reported accordingly.

It is most helpful when a good description of the problem is included in the bug report. That is, a good example of all the things you did that led to the problem and the problem itself exactly described. The best reports are those that include a full example showing how to reproduce the bug or problem.

If a program produces an error message, it is very important to include the message in your report! If we try to search for something from the archives using programs, it is better that the error message reported exactly matches the one that the program produces. (Even the case sensitivity should be observed!) You should never try to remember what the error message was; instead, copy and paste the entire message into your report!

Please include the following information in your report:

• The version number of the MySQL distribution you are using (for example, MySQL 3.22.22). You can find out which version you are running by executing mysqladmin version. mysqladmin can be found in the `bin' directory under your MySQL installation directory.
• The manufacturer and model of the machine you are working on.
• The operating system name and version. For most operating systems, you can get this information by executing the Unix command uname -a.
• Sometimes the amount of memory (real and virtual) is relevant. If in doubt, include these values.
• If you are using a source distribution of MySQL, the name and version number of the compiler used is needed. If you have a binary distribution, the distribution name is needed.
• If the problem occurs during compilation, include the exact error message(s) and also a few lines of context around the offending code in the file where the error occurred.
• If any database table is related to the problem, include the output from mysqldump --no-data db_name tbl_name1 tbl_name2 ... This is very easy to do and is a powerful way to get information about any table in a database that will help us create a situation matching the one you have.
• For speed-related bugs or problems with SELECT statements, you should always include the output of EXPLAIN SELECT ..., and at least the number of rows that the SELECT statement produces. The more information you give about your situation, the more likely it is that someone can help you! For example, the following is an example of a very good bug report (it should of course be posted with the mysqlbug script): Example run under the mysql command line tool:

  mysql> SHOW VARIABLES;
  mysql> EXPLAIN SELECT ...
         <output-from-EXPLAIN>
  mysql> FLUSH STATUS;
  mysql> SELECT ...
         <A short version of the output from SELECT,
         including the time taken to run the query>
  mysql> SHOW STATUS;
         <output from SHOW STATUS>
  

• If a bug or problem occurs while running MySQL, try to provide an input script that will reproduce the anomaly. This script should include any necessary source files. The more closely the script can reproduce your situation, the better. If you can't provide a script, you should at least include the output from mysqladmin variables extended-status processlist in your mail to provide some information of how your system is performing!
• If you think that MySQL produces a strange result from a query, include not only the result, but also your opinion of what the result should be and an account describing the basis for your opinion.
• When giving an example of the problem, it's better to use the variable names, table names, etc., that exist in your actual situation than to come up with new names. The problem could be related to the name of a variable, table, etc.! These cases are rare, perhaps, but it is better to be safe than sorry. After all, it should be easier for you to provide an example that uses your actual situation and it is by all means better for us. In case you have data you don't want to show to others, you can use ftp to transfer it to ftp://www.mysql.com/pub/mysql/secret/. If the data are really top secret and you don't want to show them even to us, then go ahead and provide an example using other names, but please regard this as the last choice.
• Include all the options given to the relevant programs, if possible. For example, indicate the options that you use when you start the mysqld daemon and that you use to run any MySQL client programs. The options to programs like mysqld and mysql, and to the configure script are often keys to answers and very relevant! It is never a bad idea to include them anyway! If you use any modules, such as Perl or PHP, please include the version number(s) of those as well.
• If you can't produce a test case in a few rows, or if the test table is too big to be mailed to the mailing list (more than 10 rows), you should dump your tables using mysqldump and create a `README' file that describes your problem. Create a compressed archive of your files using tar and gzip or zip, and use ftp to transfer the archive to ftp://www.mysql.com/pub/mysql/secret/. Then send a short description of the problem to
• If your question is related to the privilege system, please include the output of mysqlaccess, the output of mysqladmin reload and all the error messages you get when trying to connect! When you test your privileges, you should first run mysqlaccess. After this, execute mysqladmin reload version, and last you should try to connect with the program that gives you trouble. mysqlaccess can be found in the `bin' directory under your MySQL installation directory.
• If you have a patch for a bug, that is good. But don't assume the patch is all we need or that we will use it even if you don't provide some necessary information such as test cases showing the bug that your patch fixes. We might find problems with your patch or we might not understand it at all; if so, we can't use it. If we can't verify exactly what the patch is meant for, we won't use it. Test cases will help us here. Show that the patch will handle all the situations that may occur. If we find a borderline case (even a rare one) where the patch won't work, the patch may be useless.
• Guesses about what the bug is, why it occurs, or what it depends on, are usually wrong. Even we can't guess such things without first using a debugger to determine the real cause of a bug.
• Indicate in your mail message that you have checked the reference manual and mail archive so others know that you have tried to solve your problem yourself.
• If you get a parse error, please check your syntax closely! If you can't find something wrong with it, it's extremely likely that your current version of MySQL doesn't support the query you are using. If you are using the current version and the manual at http://www.mysql.com/doc.html doesn't cover the syntax you are using, MySQL doesn't support your query. In this case, your only options are to implement the syntax yourself or email If the manual covers the syntax you are using, but you have an older version of MySQL, you should check the MySQL change history to see when the syntax was implemented. See section D MySQL change history. In this case, you have the option of upgrading to a newer version of MySQL.
• If you have a problem such that your data appears corrupt or you get errors when you access some particular table, you should first check and then try repairing your tables with isamchk. See section 13 Maintaining a MySQL installation.
• If you often get corrupted tables you should try to find out when and why this happens! In this case, the `mysql-data-directory/'hostname'.err' file may contain some information about what happened. Please include any relevant information from this file in your bug report! Normally mysqld should NEVER crash a table if nothing killed it in the middle of an update! If you can find the source of why mysqld dies, it's much easier for us to provide you with a fix for the problem!
• If possible, download the most recent version of MySQL and check whether or not it solves your problem. All versions of MySQL are thoroughly tested and should work without problems! We believe in making everything as backward compatible as possible and you should be able to switch MySQL versions in minutes! See section 4.3 Which MySQL version to use.

If you are a support customer, please cross-post the bug report to the appropriate mailing list to see if someone else has experienced (and perhaps solved) the problem.

For information on reporting bugs in MyODBC, see section 16.2 How to report problems with MyODBC.

For solutions to some common problems, see See section 18 Problems and common errors.

When answers are sent to you individually and not to the mailing list, it is considered good etiquette to summarize the answers and send the summary to the mailing list so that others may have the benefit of responses you received that helped you solve your problem!

2.4 Guidelines for answering questions on the mailing list

If you consider your answer to have broad interest, you may want to post it to the mailing list instead of replying directly to the individual who asked. Try to make your answer general enough that people other than the original poster may benefit from it. When you post to the list, please make sure that your answer is not a duplication of a previous answer.

Try to summarize the essential part of the question in your reply; don't feel obliged to quote the entire original message.

Please don't post mail messages from your browser with HTML mode turned on! Many users doesn't read mail with a browser!

3 MySQL licensing and support

This chapter describes MySQL licensing and support arrangements, including:

• Our licensing policies for non-Microsoft and Microsoft operating systems
• The copyrights under which MySQL is distributed (see section 3.2 Copyrights used by MySQL)
• Sample situations illustrating when a license is required (see section 3.4 Example licensing situations)
• Licensing and support costs (see section 3.5 MySQL licensing and support costs), and support benefits (see section 3.6 Types of commercial support)

3.1 MySQL licensing policy

The formal terms of the license for non-Microsoft operating systems such as Unix or OS/2 are specified in section J The MySQL server license for non Microsoft operating systems. Basically, our licensing policy is as follows:

• For normal internal use, MySQL generally costs nothing. You do not have to pay us if you do not want to.
• A license is required if:
  • You sell the MySQL server directly or as a part of another product or service
  • You charge for installing and maintaining a MySQL server at some client site
  • You include MySQL in a distribution that is non redistributable and you charge for some part of that distribution
• For circumstances under which a MySQL license is required, you need a license per machine that runs the mysqld server. However, a multiple-CPU machine counts as a single machine, and there is no restriction on the number of MySQL servers that run on one machine, or on the number of clients concurrently connected to a server running on that machine!
• You do not need a license to include client code in commercial programs. The client access part of MySQL is in the public domain. The mysql command line client includes code from the readline library that is under the GNU Public License.
• For customers who have purchased 10 licenses or a high enough level of support, we provide additional functionality. Currently, this means we provide the pack_isam utility for creating fast compressed read-only databases. (The server includes support for reading such databases but not the packing tool used to create them.) If support agreements generate sufficient revenue, we will probably release this tool under the same license as the MySQL server.
• If your use of MySQL does not require a license, but you like MySQL and want to encourage further development, you are certainly welcome to purchase a license anyway.
• If you use MySQL in a commercial context such that you profit by its use, we ask that you further the development of MySQL by purchasing some level of support. We feel that if MySQL helps your business, it is reasonable to ask that you help MySQL. (Otherwise, if you ask us support questions, you are not only using for free something into which we've put a lot a work, you're asking us to provide free support, too.)

For use under Microsoft operating systems (Win95/Win98/WinNT), you need a MySQL license after a trial period of 30 days, with the exception that licenses may be obtained upon request at no cost for educational use or for university- or government-sponsored research settings. See section K The MySQL license for Microsoft operating systems. A shareware version of MySQL-Win32 that you can try before buying is available at http://www.mysql.com/mysql_w32.htmy. After you have paid, you will get a password that will enable you to access the newest MySQL-Win32 version.

If you have any questions as to whether or not a license is required for your particular use of MySQL, please contact us. See section 3.5.2 Contact information.

If you require a MySQL license, the easiest way to pay for it is to use the license form at TcX's secure server at https://www.mysql.com/license.htmy. Other forms of payment are discussed in section 3.5.1 Payment information.

3.2 Copyrights used by MySQL

There are several different copyrights on the MySQL distribution:

1. The MySQL-specific source needed to build the mysqlclient library and programs in the `client' directory is in the public domain. Each file that is in the public domain has a header which clearly states so. This includes everything in the `client' directory and some parts of the mysys, mystring and dbug libraries.
2. Some small parts of the source (GNU getopt) are covered by the "GNU LIBRARY LIBRARY GENERAL PUBLIC LICENSE". See the `mysys/COPYING.LIB' file.
3. Some small parts of the source (GNU readline) are covered by the "GNU GENERAL PUBLIC LICENSE". See the `readline/COPYING' file.
4. Some parts of the source (the regexp library) are covered by a Berkeley style copyright.
5. The other source needed for the MySQL server on non-Microsoft platforms is covered by the "MySQL FREE PUBLIC LICENSE", which is based on the "Aladdin FREE PUBLIC LICENSE." See section J The MySQL server license for non Microsoft operating systems. When running MySQL on any Microsoft operating system, other licensing applies.

The following points set forth the philosophy behind our copyright policy:

• The SQL client library should be totally free so that it can be included in commercial products without limitations.
• People who want free access to the software into which we have put a lot of work can have it, so long as they do not try to make money directly by distributing it for profit.
• People who want the right to keep their own software proprietary, but also want the value from our work, can pay for the privilege.
• That means normal in-house use is FREE. But if you use MySQL for something important to you, you may want to help further its development by purchasing a license or a support contract. See section 3.6 Types of commercial support.

3.2.1 Possible future copyright changes

We may choose to distribute older versions of MySQL with the GPL in the future. However, these versions will be identified as GNU MySQL. Also, all copyright notices in the relevant files will be changed to the GPL.

3.3 Distributing MySQL commercially

This section is a clarification of the license terms that are set forth in the "MySQL FREE PUBLIC LICENSE" (FPL). See section J The MySQL server license for non Microsoft operating systems.

MySQL may be used freely, including by commercial entities for evaluation or unsupported internal use. However, distribution for commercial purposes of MySQL, or anything containing or derived from MySQL in whole or in part, requires a written commercial license from TcX AB, the sole entity authorized to grant such licenses.

You may not include MySQL "free" in a package containing anything for which a charge is being made, except as noted below.

The intent of the exception provided in the second clause of the license is to allow commercial organizations operating an FTP server or a bulletin board to distribute MySQL freely from it, provided that:

1. The organization complies with the other provisions of the FPL, which include among other things a requirement to distribute the full source code of MySQL and of any derived work, and to distribute the FPL itself along with MySQL;
2. The only charge for downloading MySQL is a charge based on the distribution service and not one based on the content of the information being retrieved (i.e., the charge would be the same for retrieving a random collection of bits of the same size);
3. The server or BBS is accessible to the general public, i.e., the phone number or IP address is not kept secret, and anyone may obtain access to the information (possibly by paying a subscription or access fee that is not dependent on or related to purchasing anything else).

If you want to distribute software in a commercial context that incorporates MySQL and you do not want to meet these conditions, you should contact TcX AB to find out about commercial licensing, which involves a payment. The only ways you legally can distribute MySQL or anything containing MySQL are by distributing MySQL under the requirements of the FPL, or by getting a commercial license from TcX AB.

3.4 Example licensing situations

This section describes some situations illustrating whether or not you must license the MySQL server. Generally these examples involve providing MySQL as part of a product or service that you are selling to a customer, or requiring that MySQL be used in conjunction with your product. In such cases, it is your responsibility to obtain a license for the customer if one is necessary. (This requirement is waived if your customer already has a MySQL license. But the seller must send customer information and the license number to TcX, and the license must be a full license, not an OEM license.)

Note that a single MySQL license covers any number of CPUs/users/customers/mysqld servers on a machine!

3.4.1 Selling products that use MySQL

To determine whether or not you need a MySQL license when selling your application, you should ask whether the proper functioning of your application is contingent on the use of MySQL and whether you include MySQL with your product. There are several cases to consider:

• Does your application require MySQL to function properly? If your product requires MySQL, you need a license for any machine that runs the mysqld server. For example, if you've designed your application around MySQL, then you've really made a commercial product that requires the engine, so you need a license. If your application does not require MySQL, you need not obtain a license. For example, if MySQL just added some new optional features to your product (such as adding logging to a database if MySQL is used rather than logging to a text file), it should fall within normal use, and a license would not be required. In other words, you need a license if you sell a product designed specifically for use with MySQL or that requires the MySQL server to function at all. This is true whether or not you provide MySQL for your client as part of your product distribution. It also depends on what you're doing for the client. Do you plan to provide your client with detailed instructions on installing MySQL with your software? Then your product may be contingent on the use of MySQL; if so, you need to buy a license. If you are simply tying into a database that you expect already to have been installed by the time your software is purchased, then you probably don't need a license.
• Do you include MySQL in a distribution and charge for that distribution? If you include MySQL with a distribution that you sell to customers, you will need a license for any machine that runs the mysqld server, because in this case you are selling a system that includes MySQL. This is true whether the use of MySQL with your product is required or optional.
• Do you neither require for your product nor include MySQL with it? Suppose you want to sell a product that is designed generally to use "some database" and that can be configured to use any of several supported alternative database systems (MySQL, PostgreSQL, or something else). That is, your product does not not require MySQL, but can support any database with a base level of functionality, and you don't rely on anything that only MySQL supports. Does one of you owe us money if your customer actually does choose to use MySQL? In this case, if you don't provide, obtain or set up MySQL for the customer should the customer decide to use it, neither of you need a license. If you do perform that service, see section 3.4.2 Selling MySQL-related services.

3.4.2 Selling MySQL-related services

If you perform MySQL installation on a client's machine and any money changes hands for the service (directly or indirectly), then you must buy a MySQL license.

If you sell an application for which MySQL is not strictly required but can be used, a license may be indicated, depending on how MySQL is set up. Suppose your product neither requires MySQL nor includes it in your product distribution, but can be configured to use MySQL for those customers who so desire. (This would be the case, for example, if your product can use any of a number of database engines.)

If the customer obtains and installs MySQL, no license is needed. If you perform that service for your customer, then a license is needed because then you are selling a service that includes MySQL.

3.4.3 ISP MySQL services

Internet Service Providers (ISPs) often host MySQL servers for their customers.

If you are an ISP that allows customers to install and administer MySQL for themselves on your machine with no assistance from you, neither you nor your customer need a MySQL license.

If you charge for MySQL installation and administrative support as part of your customer service, then you need a license because you are selling a service that includes MySQL.

3.4.4 Running a web server using MySQL

If you use MySQL in conjunction with a web server, you don't have to pay for a license.

This is true even if you run a commercial web server that uses MySQL, since you are not selling MySQL itself. However, in this case we would like you to purchase MySQL support, because MySQL is helping your enterprise.

3.5 MySQL licensing and support costs

Our current license prices are shown below. All prices are in US Dollars. If you pay by credit card, the currency is EURO (European Union Euro) so the prices will differ slightly.

For high volume (OEM) purchases, the following prices apply:

For OEM purchases, you must act as the middle-man for eventual problems or extension requests from your users. We also require that OEM customers have at least an extended email support contract.

If you have a low-margin high-volume product, you can always talk to us about other terms (for example, a percent of the sale price). If you do, please be informative about your product, pricing, market and any other information that may be relevant.

After buying 10 MySQL licenses, you will get a personal copy of the pack_isam utility. You are not allowed to redistribute this utility but you can distribute tables packed with it.

A full-price license is not a support agreement and includes very minimal support. This means that we try to answer any relevant question. If the answer is in the documentation, we will direct you to the appropriate section. If you have not purchased a license or support, we probably will not answer at all.

If you discover what we consider a real bug, we are likely to fix it in any case. But if you pay for support we will notify you about the fix status instead of just fixing it in a later release.

More comprehensive support is sold separately. Descriptions of what each level of support includes are given in section 3.6 Types of commercial support. Costs for the various types of commercial support are shown below. Support level prices are in EURO (European Union Euro). One EURO is about 1.17 USD.

You may upgrade from any lower level of support to a higher level of support for the difference between the prices of the two support levels.

3.5.1 Payment information

Currently we can take SWIFT payments, cheques or credit cards.

Payment should be made to:

Postgirot Bank AB
105 06 STOCKHOLM, SWEDEN

TCX DataKonsult AB
BOX 6434
11382 STOCKHOLM, SWEDEN

SWIFT address: PGSI SESS
Account number: 96 77 06 - 3

Specify: license and/or support and your name and email address.

In Europe and Japan you can use EuroGiro (that should be less expensive) to the same account.

If you want to pay by cheque, make it payable to "Monty Program KB" and mail it to the address below:

TCX DataKonsult AB
BOX 6434, Torsgatan 21
11382 STOCKHOLM, SWEDEN

If you want to pay by credit card over the Internet, you can use TcX's secure license form.

You can also print a copy of the license form, fill it in and send it by fax to:

+46-8-729 69 05

If you want us to bill you, you can use the license form and write "bill us" in the comment field. You can also mail a message to with your company information and ask us to bill you.

3.5.2 Contact information

For commercial licensing, or if you have any questions about any of the information in this section, please contact the MySQL licensing team. The much preferred method is by E-Mail to these may take much longer (Fax +46-8-729 69 05).

David Axmark
Detron HB
Kungsgatan 65 B
753 21 UPPSALA
SWEDEN
Voice Phone +46-18-10 22 80     (Timezone GMT+1. Swedish and English spoken)

3.6 Types of commercial support

3.6.1 Basic email support

Basic email support is a very inexpensive support option and should be thought of more as a way to support our development of MySQL than as a real support option.

At this support level, the MySQL mailing lists are the preferred means of communication. Questions normally should be mailed to the primary mailing list (mysql@lists.mysql.com) or one of the other regular lists (for example, mysql-win32@lists.mysql.com for Windows-related MySQL questions), as someone else already may have experienced and solved the problem you have. See section 2.2 Asking questions or reporting bugs.

However, by purchasing basic email support, you also have access to the support address mysql-support@mysql.com, which is not available as part of the minimal support that you get by purchasing a MySQL license. This means that for especially critical questions, you can cross-post your message to mysql-support@mysql.com. (If the message contains sensitive data, you should post only to mysql-support@mysql.com.)

REMEMBER! to ALWAYS include your registration number and expiration date when you send a message to

Basic email support includes the following types of service:

• If your question is already answered in the manual, we will inform you of the correct section in which you can find the answer. If the answer is not in the manual, we will point you in the right direction to solve your problem.
• We guarantee a timely answer for your email messages. We can't guarantee that we can solve any problem, but at least you will receive an answer if we can contact you by email.
• We will help with unexpected problems when you install MySQL from a binary distribution on supported platforms. This level of support does not cover installing MySQL from a source distribution. "Supported" platforms are those for which MySQL is known to work. See section 4.2 Operating systems supported by MySQL.
• We will help you with bugs and missing features. Any bugs that are found are fixed for the next MySQL release. If the bug is critical for you, we will mail you a patch for it as soon the bug is fixed. Critical bugs always have the highest priority for us, to ensure that they are fixed as soon as possible.
• Your suggestions for the further development of MySQL will be taken into consideration. By taking email support you have already helped the further development of MySQL. If you want to have more input, upgrade to a higher level of support.
• If you want us to help optimize your system, you must upgrade to a higher level of support.

3.6.2 Extended email support

Extended email support includes everything in basic email support with these additions:

• Your email will be dealt with before mail from basic email support users and non-registered users.
• Your suggestions for the further development of MySQL will receive strong consideration. Simple extensions that suit the basic goals of MySQL are implemented in a matter of days. By taking extended email support you have already helped the further development of MySQL.
• We include a binary version of the pack_isam packing tool for creating fast compressed read-only databases (it does not support BLOB or TEXT types yet). The current server includes support for reading such databases but not the packing tool used to create them.
• Typical questions that are covered by extended email support are:
  • We will answer and (within reason) solve questions that relate to possible bugs in MySQL. As soon as the bug is found and corrected, we will mail a patch for it.
  • We will help with unexpected problems when you install MySQL from a source or binary distribution on supported platforms.
  • We will answer questions about missing features and offer hints how to work around them.
  • We will provide hints on optimizing mysqld for your situation.
• You are allowed to influence the priority of items on the MySQL TODO. This will ensure that the features you really need will be implemented sooner than they might be otherwise.

3.6.3 Login support

Login support includes everything in extended email support with these additions:

• Your email will be dealt with even before mail from extended email support users.
• Your suggestions for the further development of MySQL will be taken into very high consideration. Realistic extensions that can be implemented in a couple of hours and that suit the basic goals of MySQL will be implemented as soon as possible.
• If you have a very specific problem, we can try to log in on your system to solve the problem "in place."
• Like any database vendor, we can't guarantee that we can rescue any data from crashed tables, but if the worst happens we will help you rescue as much as possible. MySQL has proven itself very reliable, but anything is possible due to circumstances beyond our control (for example, if your system crashes or someone kills the server by executing a kill -9 command).
• We will provide hints on optimizing your system and your queries.
• You are allowed to call a MySQL developer (in moderation) and discuss your MySQL-related problems.

3.6.4 Extended login support

Extended login support includes everything in login support with these additions:

• Your email has the highest possible priority.
• We will actively examine your system and help you optimize it and your queries. We may also optimize and/or extend MySQL to better suit your needs.
• You may also request special extensions just for you. For example:

  mysql> select MY_CALCULATION(col_name1,col_name2) from tbl_name;
  

• We will provide a binary distribution of all important MySQL releases for your system, as long as we can get an account on a similar system. In the worst case, we may require access to your system to be able to create a binary distribution.
• If you can provide accommodations and pay for traveler fares, you can even get a MySQL developer to visit you and offer you help with your troubles. Extended login support entitles you to one personal encounter per year, but we are as always very flexible towards our customers!

4 Installing MySQL

This chapter describes how to obtain and install MySQL:

• For a list of sites from which you can obtain MySQL, see section 4.1 How to get MySQL.
• To see which platforms are supported, see section 4.2 Operating systems supported by MySQL.
• Several versions of MySQL are available, in both binary and source distributions. To determine which version and type of distribution you should use, see section 4.4 How and when updates are released.
• Installation instructions for binary and source distributions are described in section 4.6 Installing a MySQL binary distribution, and section 4.7 Installing a MySQL source distribution. Each set of instructions includes a section on system-specific problems you may run into.
• For post-installation procedures, see section 4.15 Post-installation setup and testing. These procedures apply whether you install MySQL using a binary or source distribution.

4.1 How to get MySQL

Check the MySQL home page for information about the current version and for downloading instructions.

However, the Internet connection at TcX is not so fast; we would prefer that you do the actual downloading from one of the mirror sites listed below.

Please report bad or out of date mirrors to webmaster@mysql.com.

Europe:

• Austria [Univ. of Technology/Vienna] WWW FTP
• Bulgaria [Naturella] FTP
• Croatia [HULK] WWW FTP
• Czech Republic [Masaryk University in Brno] WWW FTP
• Czech Republic [www.sopik.cz] WWW
• Denmark [Ake] WWW
• Denmark [SunSITE] WWW FTP
• Estonia [OKinteractive] WWW
• France [minet] WWW
• Finland [EUnet] WWW
• Finland [clinet] FTP
• Germany [Bonn University, Bonn] WWW FTP
• Germany [Wolfenbuettel] WWW FTP
• Germany [Staufen] WWW
• Germany [Cable & Wireless] FTP
• Greece [NTUA, Athens] WWW FTP
• Italy [Teta Srl] WWW
• Poland [Sunsite] WWW FTP
• Portugal [lerianet] WWW FTP
• Russia [DirectNet] WWW
• Russia [IZHCOM] WWW FTP
• Russia [Scientific Center/Chernogolovka] FTP
• Romania [Timisoara] WWW FTP
• Romania [Bucharest] WWW FTP
• Spain [MasterD] WWW
• Sweden [Sunet] WWW FTP
• Switzerland [Sunsite] WWW FTP
• UK [Omnipotent/UK] WWW FTP
• UK [PLiG/UK] WWW FTP
• UK [SunSITE] WWW FTP
• Ukraine [PACO] WWW FTP

North America:

• Canada [Tryc] WWW
• Canada [Cyberus] WWW FTP
• USA [Hurricane Electric/San Jose] WWW
• USA [Netcasting/West Coast] FTP
• USA [Circle Net/North Carolina] WWW
• USA [Gina net/Florida] WWW
• USA [pingzero/Los Angeles] WWW
• USA [Wisconsin University/Wisconsin] WWW FTP
• USA [DIGEX] FTP

South America:

• Brazil [Matrix] WWW
• Chile [Vision] WWW

Asia:

• China [Freecode] WWW
• Korea [KREONet] WWW
• Japan [Soft Agency] WWW
• Japan [Nagoya Syouka University] WWW FTP
• Singapore [HJC] WWW FTP
• Taiwan [HT] WWW

Australia:

• Australia [AARNet/Queensland] WWW FTP
• Australia [Tas] WWW FTP
• Australia [Blue Planet/Melbourne] WWW
• Australia [ITworks Consulting/Victoria] WWW

Africa:

• South-Africa [Mweb/] WWW
• South-Africa [The Internet Solution/Johannesburg] FTP

4.2 Operating systems supported by MySQL

We use GNU Autoconf so it is possible to port MySQL to all modern systems with working Posix threads and a C++ compiler. (To compile only the client code, a C++ compiler is required but not threads.) We use and develop the software ourselves primarily on Sun Solaris (versions 2.5 & 2.6) and to a lesser extent on RedHat Linux 5.0.

MySQL has been reported to compile sucessfully on the following operating system/thread package combinations. Note that for many operating systems, the native thread support works only in the latest versions.

• AIX 4.x with native threads
• BSDI 2.x with the included MIT-pthreads package
• BSDI 3.0, 3.1 and 4.x with native threads
• DEC UNIX 4.x with native threads
• FreeBSD 2.x with the included MIT-pthreads package
• FreeBSD 3.x with native threads
• HP-UX 10.20 with the included MIT-pthreads package
• HP-UX 11.x with the native threads.
• Linux 2.0+ with LinuxThreads 0.7.1 or glibc 2.0.7
• NetBSD 1.3/1.4 Intel and NetBSD 1.3 Alpha (Requires GNU make)
• OpenBSD 2.x with the included MIT-pthreads package
• OS/2 Warp 3, FixPack 29 and OS/2 Warp 4, FixPack 4
• SGI Irix 6.x with native threads
• Solaris 2.5, 2.6 and 2.7 with native threads on SPARC and x86
• SunOS 4.x with the included MIT-pthreads package
• SCO OpenServer with a recent port of the FSU Pthreads package
• SCO UnixWare 7.0.1
• Tru64 Unix
• Win95, Win98 and NT (the newest version is currently available only for users with a MySQL license or MySQL email support). For those who wish to test before they buy, we have released MySQL 3.21.29 (an older version) as shareware.

4.3 Which MySQL version to use

The first decision to make is whether you want to use the latest development release or the last stable release:

• Normally, if you are beginning to use MySQL for the first time or trying to port it to some system for which there is no binary distribution, we recommend going with the development release (currently 3.22.x). This is because there are usually no really serious bugs in the development release, and you can easily test it on your machine with the crash-me and benchmark tests. See section 11 The MySQL benchmark suite.
• Otherwise, if you are running an old system and want to upgrade, but don't want to take chances with 3.22, you should upgrade to 3.21.33. We have tried to fix only fatal bugs and make small, relatively safe changes to that version.

The second decision to make is whether you want to use a source distribution or a binary distribution:

• If you want to run MySQL on a platform for which a current binary distribution exists, use that. Generally, it will be easier to install than a source distribution.
• If you want to read (and/or modify) the C and C++ code that makes up MySQL, you should get a source distribution. The source code is always the ultimate manual. Source distributions also contain more tests and examples than binary distributions.

The MySQL naming scheme uses release numbers that consist of three numbers and a suffix. For example, a release name like mysql-3.21.17-beta is interpreted like this:

• The first number (3) describes the file format. All version 3 releases have the same file format. When a version 4 appears, every table will have to be converted to the new format (nice tools for this will be included, of course).
• The second number (21) is the release level. Normally there are two to choose from. One is the release/stable branch (currently 21) and the other is the development branch (currently 22) . Normally both are stable, but the development version may have quirks, missing documentation on new features or may fail to compile on some systems.
• The third number (17) is the version number within the release level. This is incremented for each new distribution. Usually you want the latest version for the release level you have choosen.
• The suffix (beta) indicates the stability level of the release. The possible suffixes are:
  • alpha indicates that the release contains some large section of new code that hasn't been 100% tested. Known bugs (usually there are none) should be documented in the News section. See section D MySQL change history. There are also new commands and extensions in most alpha releases.
  • beta means that all new code has been tested. No major new features were added. There should be no known bugs.
  • gamma is a beta that has been around a while and seems to work fine. This is what many other companies call a release.
  • If there is no suffix, it means that the version has been run for a while at many different sites with no reports of bugs other than platform-specific bugs. This is what we call a stable release.

All versions of MySQL are run through our standard tests and benchmarks to ensure that they are relatively safe to use. Since the standard tests are extended over time to check for all previously found bugs, the test suite keeps getting better.

Note that all releases have been tested at least with:

An internal test suite

This is part of a production system for a customer. It has many tables with hundreds of megabytes of data.

The MySQL benchmark suite

This runs a range of common queries. It is also a test to see whether the latest batch of optimizations actually made the code faster. See section 11 The MySQL benchmark suite.

The crash-me test

This tries to determine what features the database supports and what its capabilities and limitations are. See section 11 The MySQL benchmark suite.

Another test is that we use the newest MySQL version in our internal production environment, on at least one machine. We have more than 100 gigabytes of data to work with.

4.4 How and when updates are released

MySQL is evolving quite rapidly here at TcX and we want to share this with other MySQL users. We try to make a release when we have very useful features that others seem to have a need for.

We also try to help out users who request features that are easy to implement. We also take note of what our licensed users want to have and we especially take note of what our extended email supported customers want and try to help them out.

No one has to download a new release. The News section will tell you if the new release has something you really want. See section D MySQL change history.

We use the following policy when updating MySQL:

• For each minor update, the last number in the version string is incremented. When there are major new features or minor incompatibilities with previous versions, the second number in the version string is incremented. When the file format changes, the first number is increased.
• Stable tested releases are meant to appear about 1-2 times a year, but if small bugs are found, a release with only bug-fixes will be released.
• Working releases are meant to appear about every 1-8 weeks.
• Binary distributions for some platforms will be made by us for major releases. Other people may make binary distributions for other systems but probably less frequently.
• We usually make patches available as soon as we have located and fixed small bugs.
• For non-critical but annoying bugs, we will make patches available if they are sent to us. Otherwise we will combine many of them into a larger patch.
• If there is, by any chance, a fatal bug in a release we will make a new release as soon as possible. We would like other companies to do this, too. :)

The current stable release is 3.22; We have already moved active development to 3.23. Bugs will still be fixed in the stable version. We don't believe in a complete freeze, as this also leaves out bug fixes and things that "must be done". "Somewhat frozen" means that we may add small things that "almost surely will not affect anything that's already working".

4.5 Installation layouts

This section describes the default layout of the directories created by installing binary and source distributions.

A binary distribution is installed by unpacking it at the installation location you choose (typically `/usr/local/mysql') and creates the following directories in that location:

A source distribution is installed after you configure and compile it. By default, the installation step installs files under `/usr/local', in the following subdirectories:

Within an installation directory, the layout of a source installation differs from that of a binary installation in the following ways:

• The mysqld server is installed in the `libexec' directory rather than in the `bin' directory.
• The data directory is `var' rather than `data'.
• mysql_install_db is installed in the `/usr/local/bin' directory rather than in `/usr/local/mysql/scripts'.
• The header file and library directories are `include/mysql' and `lib/mysql' rather than `include' and `lib'.

4.6 Installing a MySQL binary distribution

You need the following tools to install a MySQL binary distribution:

• GNU gunzip to uncompress the distribution.
• A reasonable tar to unpack the distribution. GNU tar is known to work.

An alternative installation method under Linux is to use RPM (RedHat Package Manager) distributions. See section 4.6.1 Linux RPM notes.

If you run into problems, PLEASE ALWAYS USE mysqlbug when posting questions to mysql@lists.mysql.com. Even if the problem isn't a bug, mysqlbug gathers system information that will help others solve your problem. By not using mysqlbug, you lessen the likelihood of getting a solution to your problem! You will find mysqlbug in the `bin' directory after you unpack the distribution. See section 2.3 How to report bugs or problems.

The basic commands you must execute to install and use a MySQL binary distribution are:

shell> gunzip < mysql-VERSION-OS.tar.gz | tar xvf -
shell> ln -s mysql-VERSION-OS mysql
shell> cd mysql
shell> scripts/mysql_install_db
shell> bin/safe_mysqld &

You can add new users using the bin/mysql_setpermission script if you install the DBI and Msql-Mysql-modules Perl modules.

Here follows a more detailed description:

To install a binary distribution, follow the steps below, then proceed to section 4.15 Post-installation setup and testing, for post-installation setup and testing:

1. Pick the directory under which you want to unpack the distribution, and move into it. In the example below, we unpack the distribution under `/usr/local' and create a directory `/usr/local/mysql' into which MySQL is installed. (The following instructions therefore assume you have permission to create files in `/usr/local'. If that directory is protected, you will need to perform the installation as root.)
2. Obtain a distribution file from one of the sites listed in section 4.1 How to get MySQL. MySQL binary distributions are provided as compressed tar archives and have names like `mysql-VERSION-OS.tar.gz', where VERSION is a number (e.g., 3.21.15), and OS indicates the type of operating system for which the distribution is intended (e.g., pc-linux-gnu-i586).
3. Unpack the distribution and create the installation directory:

   shell> gunzip < mysql-VERSION-OS.tar.gz | tar xvf -
   shell> ln -s mysql-VERSION-OS mysql
   

   The first command creates a directory named `mysql-VERSION-OS'. The second command makes a symbolic link to that directory. This lets you refer more easily to the installation directory as `/usr/local/mysql'.
4. Change into the installation directory:

   shell> cd mysql
   

   You will find several files and subdirectories in the mysql directory. The most important for installation purposes are the `bin' and `scripts' subdirectories.

   `bin'

   This directory contains client programs and the server You should add the full pathname of this directory to your PATH environment variable so that your shell finds the MySQL programs properly.

   `scripts'

   This directory contains the mysql_install_db script used to initialize the server access permissions.

5. If you would like to use mysqlaccess and have the MySQL distribution in some nonstandard place, you must change the location where mysqlaccess expects to find the mysql client. Edit the `bin/mysqlaccess' script at approximately line 18. Search for a line that looks like this:

   $MYSQL     = '/usr/local/bin/mysql';    # path to mysql executable
   

   Change the path to reflect the location where mysql actually is stored on your system. If you do not do this, you will get a broken pipe error when you run mysqlaccess.
6. Create the MySQL grant tables (necessary only if you haven't installed MySQL before):

   shell> scripts/mysql_install_db
   

   Note that MySQL versions older than 3.22.10 started the MySQL server when you run mysql_install_db. This is no longer true!
7. If you want to install support for the Perl DBI/DBD interface, see section 4.10 Perl installation comments.
8. If you would like MySQL to start automatically when you boot your machine, you can copy support-files/mysql.server to the location where your system has its startup files. More information can be found in the support-files/mysql.server script itself, and in section 4.15.3 Starting and stopping MySQL automatically.

After everything has been unpacked and installed, you should initialize and test your distribution.

You can start the MySQL server with the following command:

shell> bin/safe_mysqld &

See section 4.15 Post-installation setup and testing.

4.6.1 Linux RPM notes

The recommended way to install MySQL on Linux is by using an RPM file. The MySQL RPMs are currently being built on a RedHat 5.2 system but should work on other versions of Linux that support rpm and use glibc.

If you have problems with an RPM file, for example Sorry, the host 'xxxx' could not be looked up, see section 4.6.3.1 Linux notes.

The RPM files you may want to use are:

• MySQL-VERSION.i386.rpm The MySQL server. You will need this unless you only want to connect to another MySQL server running on another machine.
• MySQL-client-VERSION.i386.rpm The standard MySQL client programs. You probably always want to install this package.
• MySQL-bench-VERSION.i386.rpm Tests and benchmarks. Requires Perl and msql-mysql-modules RPMs.
• MySQL-devel-VERSION.i386.rpm Libraries and include files needed if you want to compile other MySQL clients, such as the Perl modules.
• MySQL-VERSION.src.rpm This contains the source code for all of the above packages. It can also be used to try to build RPMs for other architectures (for example, Alpha or SPARC).

To see all files in an RPM package:

shell> rpm -qpl MySQL-VERSION.i386.rpm

To perform a standard minimal installation, run this command:

shell> rpm -i MySQL-VERSION.i386.rpm MySQL-client-VERSION.i386.rpm

To install just the client package:

shell> rpm -i MySQL-client-VERSION.i386.rpm

The RPM places data in `/var/lib/mysql'. The RPM also creates the appropriate entries in `/sbin/rc.d/' to start the server automatically at boot time. (This means that if you have performed a previous installation, you may want to make a copy of your previously-installed MySQL startup file if you made any changes to it, so you don't lose your changes.)

After installing the RPM file(s), go to the binary install section and use the instructions there, starting from the step that creates the MySQL grant tables. See section 4.6 Installing a MySQL binary distribution.

4.6.2 Building client programs

If you compile MySQL clients that you've written yourself or that you obtain from a third party, they must be linked using the -lmysqlclient option on the link command. You may also need to specify a -L option to tell the linker where to find the library. For example, if the library is installed in `/usr/local/mysql/lib', use -L/usr/local/mysql/lib -lmysqlclient on the link command.

For clients that use MySQL header files, you may need to specify a -I option when you compile them (for example, -I/usr/local/mysql/include), so the compiler can find the header files.

4.6.3 System-specific issues

The following sections indicate some of the issues that have been observed to occur on particular systems when installing MySQL from a binary distribution.

4.6.3.1 Linux notes

MySQL needs at least Linux 2.0.

The binary release is linked with -static, which means you not normally need not worry about which version of the system libraries you have. You need not install LinuxThreads, either. A program linked with -static is slightly bigger than a dynamically-linked program but also slightly faster (3-5%). One problem however is that you can't use user definable functions (UDFs) with a statically-linked program. If you are going to write or use UDF functions (this is something only for C or C++ programmers) you must compile MySQL yourself, using dynamic linking.

If you are using a libc-based system (instead of a glibc2 system), you will probably get some problems with hostname resolving and getpwnam() with the binary release. (This is because glibc unfortunately depends on some external libraries to resolve hostnames and getwpent() , even when compiled with -static). In this case you probably get the following error message when you run mysql_install_db:

Sorry, the host 'xxxx' could not be looked up

or the following error when you try to run mysqld with the --user option:

getpwnam: No such file or directory

You can solve this problem one of the following ways:

• Get a MySQL source distribution (an RPM or the tar distribution) and install this instead.
• Execute mysql_install_db --force; This will not execute the resolveip test in mysql_install_db. The downside is that you can't use host names in the grant tables; you must use IP numbers instead (except for localhost). If you are using an old MySQL release that doesn't support --force you have to remove the resolveip test in mysql_install with an editor.
• Start mysqld with su instead of using --user.

The Linux-Intel binary and RPM releases of MySQL are configured for the highest possible speed. We are always trying to use the fastest stable compiler available.

MySQL Perl support requires Perl 5.004_03 or newer.

4.6.3.2 HP-UX notes

The binary distribution of MySQL for HP-UX is distributed as an HP depot file and as a tar file. To use the depot file you must be running at least HP-UX 10.x to have access to HP's software depot tools.

The HP version of MySQL was compiled on an HP 9000/8xx server under HP-UX 10.20, and uses MIT-pthreads. It is known to work well under this configuration. MySQL 3.22.26 and newer can also be built with HP's native thread package.

Other configurations that may work:

• HP 9000/7xx running HP-UX 10.20+
• HP 9000/8xx running HP-UX 10.30

The following configurations almost definitely won't work:

• HP 9000/7xx or 8xx running HP-UX 10.x where x < 2
• HP 9000/7xx or 8xx running HP-UX 9.x

To install the distribution, use one of the commands below, where /path/to/depot is the full pathname of the depot file:

• To install everything, including the server, client and development tools:

  shell> /usr/sbin/swinstall -s /path/to/depot mysql.full
  

• To install only the server:

  shell> /usr/sbin/swinstall -s /path/to/depot mysql.server
  

• To install only the client package:

  shell> /usr/sbin/swinstall -s /path/to/depot mysql.client
  

• To install only the development tools:

  shell> /usr/sbin/swinstall -s /path/to/depot mysql.developer
  

The depot places binaries and libraries in `/opt/mysql' and data in `/var/opt/mysql'. The depot also creates the appropriate entries in `/sbin/init.d' and `/sbin/rc2.d' to start the server automatically at boot time. Obviously, this entails being root to install.

To install the HP-UX tar distribution, you must have a copy of GNU tar.

4.7 Installing a MySQL source distribution

You need the following tools to build and install MySQL from source:

• GNU gunzip to uncompress the distribution.
• A reasonable tar to unpack the distribution. GNU tar is known to work.
• A working ANSI C++ compiler. gcc >= 2.8.1, egcs >= 1.0.2, SGI C++ and SunPro C++ are some of the compilers that are known to work. libg++ is not needed when using gcc. gcc 2.7.x has a bug that makes it impossible to compile some perfectly legal C++ files, such as `sql/sql_base.cc'. If you only have gcc 2.7.x, you must upgrade your gcc to be able to compile MySQL.
• A good make program. GNU make is always recommended and is sometimes required. If you have problems, we recommend trying GNU make 3.75 or newer.

If you run into problems, PLEASE ALWAYS USE mysqlbug when posting questions to mysql@lists.mysql.com. Even if the problem isn't a bug, mysqlbug gathers system information that will help others solve your problem. By not using mysqlbug, you lessen the likelihood of getting a solution to your problem! You will find mysqlbug in the `scripts' directory after you unpack the distribution. See section 2.3 How to report bugs or problems.

4.7.1 Quick installation overview

The basic commands you must execute to install a MySQL source distribution are (from an unpacked tar file):

shell> configure
shell> make
shell> make install
shell> scripts/mysql_install_db
shell> /usr/local/mysql/bin/safe_mysqld &

If you start from a source RPM, then do the following.

shell> rpm --rebuild MySQL-VERSION.src.rpm

This will make a binary RPM that you can install.

You can add new users using the bin/mysql_setpermission script if you install the DBI and Msql-Mysql-modules Perl modules.

Here follows a more detailed description:

To install a source distribution, follow the steps below, then proceed to section 4.15 Post-installation setup and testing, for post-installation initialization and testing.

1. Pick the directory under which you want to unpack the distribution, and move into it.
2. Obtain a distribution file from one of the sites listed in section 4.1 How to get MySQL. MySQL source distributions are provided as compressed tar archives and have names like `mysql-VERSION.tar.gz', where VERSION is a number like 3.22.27.
3. Unpack the distribution into the current directory:

   shell> gunzip < mysql-VERSION.tar.gz | tar xvf -
   

   This command creates a directory named `mysql-VERSION'.
4. Change into the top-level directory of the unpacked distribution:

   shell> cd mysql-VERSION
   

5. Configure the release and compile everything:

   shell> ./configure --prefix=/usr/local/mysql
   shell> make
   

   When you run configure, you might want to specify some options. Run ./configure --help for a list of options. section 4.7.3 Typical configure options, discusses some of the more useful options. If configure fails, and you are going to send mail to lines from `config.log' that you think can help solve the problem. Also include the last couple of lines of output from configure if configure aborts. Post the bug report using the mysqlbug script. See section 2.3 How to report bugs or problems. If the compile fails, see section 4.8 Problems compiling?, for help with a number of common problems.
6. Install everything:

   shell> make install
   

   You might need to run this command as root.
7. Create the MySQL grant tables (necessary only if you haven't installed MySQL before):

   shell> scripts/mysql_install_db
   

   Note that MySQL versions older than 3.22.10 started the MySQL server when you run mysql_install_db. This is no longer true!
8. If you want to install support for the Perl DBI/DBD interface, see section 4.10 Perl installation comments.
9. If you would like MySQL to start automatically when you boot your machine, you can copy support-files/mysql.server to the location where your system has its startup files. More information can be found in the support-files/mysql.server script itself, and in section 4.15.3 Starting and stopping MySQL automatically.

After everything has been installed, you should initialize and test your distribution.

You can start the MySQL server with the following command, where BINDIR is the directory in which safe_mysqld is installed (`/usr/local/bin' by default):

shell> BINDIR/safe_mysqld &

If that command fails immediately with mysqld daemon ended then you can find some information in the file `mysql-data-directory/'hostname'.err'. The likely reason is that you already have another mysqld server running. See section 19.3 Running multiple MySQL servers on the same machine.

See section 4.15 Post-installation setup and testing.

4.7.2 Applying patches

Sometimes patches appear on the mailing list or are placed in the patches area of the MySQL FTP site.

To apply a patch from the mailing list, save the message in which the patch appears in a file, change into the top-level directory of your MySQL source tree and run these commands:

shell> patch -p1 < patch-file-name
shell> rm config.cache
shell> make clean

Patches from the FTP site are distributed as plain text files or as files compressed with gzip files. Apply a plain patch as shown above for mailing list patches. To apply a compressed patch, change into the top-level directory of your MySQL source tree and run these commands:

shell> gunzip < patch-file-name.gz | patch -p1
shell> rm config.cache
shell> make clean

After applying a patch, follow the instructions for a normal source install, beginning with the ./configure step. After running the make install step, restart your MySQL server.

You may need to bring down any currently running server before you run make install. (Use mysqladmin shutdown to do this.) Some systems do not allow you to install a new version of a program if it replaces the version that is currently executing.

4.7.3 Typical configure options

The configure script gives you a great deal of control over how you configure your MySQL distribution. Typically you do this using options on the configure command line. You can also affect configure using certain environment variables. For a list of options supported by configure, run this command:

shell> ./configure --help

Some of the more commonly-used configure options are described below:

• To compile just the MySQL client libraries and client programs and not the server, use the --without-server option:

  shell> ./configure --without-server
  

  If you don't have a C++ compiler, mysql will not compile (it is the one client program that requires C++). In this case, you can remove the code in configure that tests for the C++ compiler and then run ./configure with the --without-server option. The compile step will still try to build mysql, but you can ignore any warnings about `mysql.cc'. (If make stops, try make -k to tell it to continue with the rest of the build even if errors occur.)
• If you don't want your log files and database directories located under `/usr/local/var', use a configure command something like one of these:

  shell> ./configure --prefix=/usr/local/mysql
  shell> ./configure --prefix=/usr/local \
             --localstatedir=/usr/local/mysql/data
  

  The first command changes the installation prefix so that everything is installed under `/usr/local/mysql' rather than the default of `/usr/local'. The second command preserves the default installation prefix, but overrides the default location for database directories (normally `/usr/local/var') and changes it to /usr/local/mysql/data.
• If you are using Unix and you want the MySQL socket located somewhere other than the default location (normally in the directory `/tmp' or `/var/run', use a configure command like this:

  shell> ./configure --with-unix-socket-path=/usr/local/mysql/tmp/mysql.sock
  

  Note that the given file must be an absolute pathname!
• If you want to compile statically-linked programs (e.g., to make a binary distribution, to get more speed or to work around problems with some RedHat distributions), run configure like this:

  shell> ./configure --with-client-ldflags=-all-static \
             --with-mysqld-ldflags=-all-static
  

• If you are using gcc and don't have libg++ or libstdc++ installed, you can tell configure to use gcc as your C++ compiler:

  shell> CC=gcc CXX=gcc ./configure
  

  When you use gcc as your C++ compiler, it will not attempt to link in libg++ or libstdc++. If the build fails and produces errors about your compiler or linker not being able to create the shared library `libmysqlclient.so.#' (`#' is a version number), you can work around this problem by giving the --disable-shared option to configure. In this case, configure will not build a shared libmysqlclient.so.# library.
• You can configure MySQL not to use DEFAULT column values for non-NULL columns (i.e., columns that are not allowed to be NULL). This causes INSERT statements to generate an error unless you explicitly specify values for all columns that require a non-NULL value. To suppress use of default values, run configure like this:

  shell> CXXFLAGS=-DDONT_USE_DEFAULT_FIELDS ./configure
  

• By default, MySQL uses the ISO-8859-1 (Latin1) character set. To change the default set, use the --with-charset option:

  shell> ./configure --with-charset=CHARSET
  

  CHARSET may be one of big5, cp1251, cp1257, czech, danish,dec8, dos, euc_kr, german1, hebrew, hp8, hungarian, koi8_ru, koi8_ukr, latin1, latin2, sjis, swe7, tis620, ujis, usa7, win1251 or win1251ukr. See section 9.1.1 The character set used for data and sorting. Note that if you want to change the character set, you must do a make distclean between configurations! If you want to convert characters between the server and the client, you should take a look at the SET OPTION CHARACTER SET command. See section 7.24 SET OPTION syntax. Warning: If you change character sets after having created any tables, you will have to run isamchk -r -q on every table. Your indexes may be sorted incorrectly otherwise. (This can happen if you install MySQL, create some tables, then reconfigure MySQL to use a different character set and reinstall it.)
• To configure MySQL with debugging code, use the --with-debug option:

  shell> ./configure --with-debug
  

  This causes a safe memory allocator to be included that can find some errors and that provides output about what is happening. See section G.1 Debugging a MySQL server.
• Options that pertain to particular systems can be found in the system-specific sections later in this chapter. See section 4.11 System-specific issues.

4.8 Problems compiling?

All MySQL programs compile cleanly for us with no warnings on Solaris using gcc. On other systems, warnings may occur due to differences in system include files. See section 4.9 MIT-pthreads notes, for warnings that may occur when using MIT-pthreads. For other problems, check the list below.

The solution to many problems involves reconfiguring. If you do need to reconfigure, take note of the following:

• If configure is run after it already has been run, it may use information that was gathered during its previous invocation. This information is stored in `config.cache'. When configure starts up, it looks for that file and reads its contents if it exists, on the assumption that the information is still correct. That assumption is invalid when you reconfigure.
• Each time you run configure, you must run make again to recompile. However, you may want to remove old object files from previous builds first, since they were compiled using different configuration options.

To prevent old configuration information or object files from being used, run these commands before rerunning configure:

shell> rm config.cache
shell> make clean

Alternatively, you can run make distclean.

The list below describes some of the problems compiling MySQL that have been found to occur most often:

• If you get errors when compiling `sql_yacc.cc' such as the ones shown below, you have probably run out of memory or swap space:

  Internal compiler error: program cc1plus got fatal signal 11
    or
  Out of virtual memory
    or
  Virtual memory exhausted
  

  The problem is that gcc requires huge amounts of memory to compile `sql_yacc.cc' with inline functions. Try running configure with the --with-low-memory option:

  shell> ./configure --with-low-memory
  

  This option causes -fno-inline to be added to the compile line if you are using gcc and -O0 if you are using something else. You should try the --with-low-memory option even if you have so much memory and swap space that you think you can't possibly have run out. This problem has been observed to occur even on systems with generous hardware configurations, and the --with-low-memory option usually fixes it.
• By default, configure picks c++ as the compiler name and GNU c++ links with -lg++. If you are using gcc, that behavior can cause problems during configuration such as this:

  configure: error: installation or configuration problem:
  C++ compiler cannot create executables.
  

  You might also observe problems during compilation related to g++, libg++ or libstdc++. One cause of these problems is that you may not have g++, or you may have g++ but not libg++ or libstdc++. Take a look at the `config.log' file. It should contain the exact reason why your c++ compiler didn't work! To work around these problems, you can use gcc as your C++ compiler. Try setting the environment variable CXX to "gcc -O3". For example:

  shell> CXX="gcc -O3" ./configure
  

  This works because gcc compiles C++ sources as well as g++ does, but does not link in libg++ or libstdc++ by default. Another way to fix these problems, of course, is to install g++, libg++ and libstdc++.
• If your compile fails with errors such as any of the following, you must upgrade your version of make to GNU make:

  making all in mit-pthreads
  make: Fatal error in reader: Makefile, line 18:
  Badly formed macro assignment
    or
  make: file `Makefile' line 18: Must be a separator (:
    or
  pthread.h: No such file or directory
  

  Solaris and FreeBSD are known to have troublesome make programs. GNU make version 3.75 is known to work.
• If you want to define flags to be used by your C or C++ compilers, do so by adding the flags to the CFLAGS and CXXFLAGS environment variables. You can also specify the compiler names this way using CC and CXX. For example:

  shell> CC=gcc
  shell> CFLAGS=-O6
  shell> CXX=gcc
  shell> CXXFLAGS=-O6
  shell> export CC CFLAGS CXX CXXFLAGS
  

  See section 4.14 TcX binaries, for a list of flag definitions that have been found to be useful on various systems.
• If you get an error message like this, you need to upgrade your gcc compiler:

  client/libmysql.c:273: parse error before `__attribute__'
  

  gcc 2.8.1 is known to work, but we recommend using egcs 1.0.3a or newer instead.
• If you get errors such as those shown below when compiling mysqld, configure didn't correctly detect the type of the last argument to accept(), getsockname() or getpeername():

  cxx: Error: mysqld.cc, line 645: In this statement, the referenced
       type of the pointer value "&length" is "unsigned long", which
       is not compatible with "int".
  new_sock = accept(sock, (struct sockaddr *)&cAddr, &length);
  

  To fix this, edit the `config.h' file (which is generated by configure). Look for these lines:

  /* Define as the base type of the last arg to accept */
  #define SOCKET_SIZE_TYPE XXX
  

  Change XXX to size_t or int, depending on your operating system. (Note that you will have to do this each time you run configure, since configure regenerates `config.h'.)
• The `sql_yacc.cc' file is generated from `sql_yacc.yy'. Normally the build process doesn't need to create `sql_yacc.cc', because MySQL comes with an already-generated copy. However, if you do need to recreate it, you might encounter this error:

  "sql_yacc.yy", line xxx fatal: default action causes potential...
  

  This is a sign that your version of yacc is deficient. You probably need to install bison (the GNU version of yacc) and use that instead.
• If you need to debug mysqld or a MySQL client, run configure with the --with-debug option, then recompile and link your clients with the new client library. See section G.2 Debugging a MySQL client.

4.9 MIT-pthreads notes

This section describes some of the issues involved in using MIT-pthreads.

Note that on Linux you should NOT use MIT-pthreads but install LinuxThreads! See section 4.11.5 Linux notes (all Linux versions).

If your system does not provide native thread support, you will need to build MySQL using the MIT-pthreads package. This includes most FreeBSD systems, SunOS 4.x, Solaris 2.4 and earlier, and some others. See section 4.2 Operating systems supported by MySQL.

• On most systems, you can force MIT-pthreads to be used by running configure with the --with-mit-threads option:

  shell> ./configure --with-mit-threads
  

  Building in a non-source directory is not supported when using MIT-pthreads, because we want to minimize our changes to this code.
• MIT-pthreads doesn't support the AF_UNIX protocol used to implement Unix sockets. This means that if you compile using MIT-pthreads, all connections must be made using TCP/IP (which is a little slower). If you find after building MySQL that you cannot connect to the local server, it may be that your client is attempting to connect to localhost using a Unix socket as the default. Try making a TCP/IP connection with mysql by using a host option (-h or --host) to specify the local host name explicitly.
• The checks that determine whether or not to use MIT-pthreads occur only during the part of the configuration process that deals with the server code. If you have configured the distribution using --without-server to build only the client code, clients will not know whether or not MIT-pthreads is being used and will use Unix socket connections by default. Since Unix sockets do not work under MIT-pthreads, this means you will need to use -h or --host when you run client programs.
• When MySQL is compiled using MIT-pthreads, system locking is disabled by default for performance reasons. You can tell the server to use system locking with the --use-locking option.
• Sometimes the pthread bind() command fails to bind to a socket without any error message (at least on Solaris). The result is that all connections to the server fail. For example:

  shell> mysqladmin version
  mysqladmin: connect to server at " failed;
  error: 'Can't connect to mysql server on localhost (146)'
  

  The solution to this is to kill the mysqld server and restart it. This has only happened to us when we have forced the server down and done a restart immediately.
• With MIT-pthreads, the sleep() system call isn't interruptible with SIGINT (break). This is only noticeable when you run mysqladmin --sleep. You must wait for the sleep() call to terminate before the interrupt is served and the process stops.
• When linking you may receive warning messages like these (at least on Solaris); they can be ignored:

  ld: warning: symbol `_iob' has differing sizes:
      (file /my/local/pthreads/lib/libpthread.a(findfp.o) value=0x4;
  file /usr/lib/libc.so value=0x140);
      /my/local/pthreads/lib/libpthread.a(findfp.o) definition taken
  ld: warning: symbol `__iob' has differing sizes:
      (file /my/local/pthreads/lib/libpthread.a(findfp.o) value=0x4;
  file /usr/lib/libc.so value=0x140);
      /my/local/pthreads/lib/libpthread.a(findfp.o) definition taken
  

• Some other warnings also can be ignored:

  implicit declaration of function `int strtoll(...)'
  implicit declaration of function `int strtoul(...)'
  

• We haven't gotten readline to work with MIT-pthreads. (This isn't needed, but may be interesting for someone.)

4.10 Perl installation comments

4.10.1 Installing Perl on Unix

Perl support for MySQL is provided by means of the DBI/DBD client interface. See section 20.5 MySQL Perl API. The Perl DBD/DBI client code requires Perl 5.004 or later. The interface will not work if you have an older version of Perl.

MySQL Perl support also requires that you've installed MySQL client programming support. If you installed MySQL from RPM files, client programs are in the client RPM, but client programming support is in the developer RPM. Make sure you've installed the latter RPM.

As of release 3.22.8, Perl support is distributed separately from the main MySQL distribution. If you want to install Perl support, the files you will need can be obtained from http://www.mysql.com/Contrib.

The Perl distributions are provided as compressed tar archives and have names like `MODULE-VERSION.tar.gz', where MODULE is the module name and VERSION is the version number. You should get the Data-Dumper, DBI, and Msql-Mysql-modules distributions and install them in that order. The installation procedure is shown below. The example shown is for the Data-Dumper module, but the procedure is the same for all three distributions.

1. Unpack the distribution into the current directory:

   shell> gunzip < Data-Dumper-VERSION.tar.gz | tar xvf -
   

   This command creates a directory named `Data-Dumper-VERSION'.
2. Change into the top-level directory of the unpacked distribution:

   shell> cd Data-Dumper-VERSION
   

3. Build the distribution and compile everything:

   shell> perl Makefile.PL
   shell> make
   shell> make test
   shell> make install
   

The make test command is important, because it verifies that the module is working. Note that when you run that command during the Msql-Mysql-modules installation to exercise the interface code, the MySQL server must be running or the test will fail.

It is a good idea to rebuild and reinstall the Msql-Mysql-modules distribution whenever you install a new release of MySQL, particularly if you notice symptoms such as all your DBI scripts dumping core after you upgrade MySQL.

If you don't have the right to install Perl modules in the system directory or if you to install local Perl modules, the following reference may help you:

http://www.iserver.com/support/contrib/perl5/modules.html

Look under the heading Installing New Modules that Require Locally Installed Modules.

4.10.2 Installing ActiveState Perl on Win32

To install the MySQL DBD module with ActiveState Perl on Win32, you should do the following:

• Open a DOS shell.
• If required, set the HTTP_proxy variable. For example, you might try: set HTTP_proxy=my.proxy.com:3128
• Start the PPM program: C:\perl\bin\ppm.pl
• If you have not already done so, install DBI: install DBI
• If this succeeds, install DBD::mysql: http://www.mysql.com/Contrib/ppd/DBD-mysql.ppd

If you can't get the above to work, you should instead install the MyODBC driver and connect to MySQL server through ODBC.

use DBI;
$dbh= DBI->connect("DBI:ODBC:$dsn","$user","$password") || 
  die "Got error $DBI::errstr when connecting to $dsn\n";

4.10.3 Installing the MySQL Perl distribution on Win32

The MySQL Perl distribution contains DBI, DBD:MySQL and DBD:ODBC.

• Get the Perl distribution for Win32 from http://www.mysql.com/download.html.
• Unzip the distribution in C: so that you get a `C:\PERL' directory.
• Add the directory `C:\PERL\BIN' to your path.
• Add the directory `C:\PERL\BIN\MSWin32-x86-thread' or `C:\PERL\BIN\MSWin32-x86' to your path.
• Test that perl works by executing perl -v in a DOS shell.

4.10.4 Problems using the Perl DBI/DBD interface

If Perl reports that it can't find the ../mysql/mysql.so module, then the problem is probably that Perl can't locate the shared library `libmysqlclient.so'.

You can fix this by any of the following methods:

• Compile the Msql-Mysql-modules distribution with perl Makefile.PL -static rather than perl Makefile.PL
• Copy libmysqlclient.so to the directory where your other shared libraries are located (probably `/usr/lib' or `/lib').
• On Linux you can add the pathname of the directory where libmysqlclient.so is located to the `/etc/ld.so.conf' file.
• Add the pathname of the directory where libmysqlclient.so is located to the LD_RUN_PATH environment variable.

If you get the following errors from DBD-mysql, you are probably using gcc (or using an old binary compiled with gcc):

/usr/bin/perl: can't resolve symbol '__moddi3'
/usr/bin/perl: can't resolve symbol '__divdi3'

Add -L/usr/lib/gcc-lib/... -lgcc to the link command when the `mysql.so' library gets built (check the output from make for `mysql.so' when you compile the Perl client). The -L option should specify the pathname of the directory where `libgcc.a' is located on your system.

Another cause of this problem may be that Perl and MySQL aren't both compiled with gcc. In this case, you can solve the mismatch by compiling both with gcc.

If you want to use the Perl module on a system that doesn't support dynamic linking (like SCO) you can generate a static version of Perl that includes DBI and DBD-mysql. The way this works is that you generate a version of Perl with the DBI code linked in and install it on top of your current Perl. Then you use that to build a version of Perl that additionally has the DBD code linked in, and install that.

On SCO, you must have the following environment variables set:

shell> LD_LIBRARY_PATH=/lib:/usr/lib:/usr/local/lib:/usr/progressive/lib
or
shell> LD_LIBRARY_PATH=/usr/lib:/lib:/usr/local/lib:/usr/ccs/lib:/usr/progressive/lib:/usr/skunk/lib
shell> LIBPATH=/usr/lib:/lib:/usr/local/lib:/usr/ccs/lib:/usr/progressive/lib:/usr/skunk/lib
shell> MANPATH=scohelp:/usr/man:/usr/local1/man:/usr/local/man:/usr/skunk/man:

First, create a Perl that includes a statically-linked DBI by running these commands in the directory where your DBI distribution is located:

shell> perl Makefile.PL LINKTYPE=static
shell> make
shell> make install
shell> make perl

Then you must install the new Perl. The output of make perl will indicate the exact make command you will need to execute to perform the installation. On SCO, this is make -f Makefile.aperl inst_perl MAP_TARGET=perl.

Next, use the just-created Perl to create another Perl that also includes a statically-linked DBD::mysql by running these commands in the directory where your Msql-Mysql-modules distribution is located:

shell> perl Makefile.PL LINKTYPE=static
shell> make
shell> make install
shell> make perl

Finally, you should install this new Perl. Again, the output of make perl indicates the command to use.

4.11 System-specific issues

The following sections indicate some of the issues that have been observed to occur on particular systems when installing MySQL from a source distribution.

4.11.1 Solaris notes

On Solaris, you may run into trouble even before you get the MySQL distribution unpacked! Solaris tar can't handle long file names, so you may see an error like this when you unpack MySQL:

x mysql-3.22.12-beta/bench/Results/ATIS-mysql_odbc-NT_4.0-cmp-db2,informix,ms-sql,mysql,oracle,solid,sybase, 0 bytes, 0 tape blocks
tar: directory checksum error

In this case, you must use GNU tar (gtar) to unpack the distribution. You can find a precompiled copy for Solaris at http://www.mysql.com/Downloads/.

Sun native threads work only on Solaris 2.5 and higher. For 2.4 and earlier versions, MySQL will automatically use MIT-pthreads. See section 4.9 MIT-pthreads notes.

If you get the following error from configure:

checking for restartable system calls... configure: error can not run test
programs while cross compiling

This means that you have something wrong with your compiler installation! In this case you should upgrade your compiler to a newer version. You may also be able to solve this problem by inserting the following row into the config.cache file:

ac_cv_sys_restartable_syscalls=${ac_cv_sys_restartable_syscalls='no'}

If you are using Solaris on a SPARC, the recommended compiler is egcs 1.1.2 or newer. You can find this at http://egcs.cygnus.com/. Note that egs 1.1.1 and gcc 2.8.1 don't work reliably on SPARC!

The recommended configure line when using egcs 1.1.2 is:

shell> CC=gcc CFLAGS="-O6" \
       CXX=gcc CXXFLAGS="-O6 -felide-constructors -fno-exceptions -fno-rtti" \
       ./configure --prefix=/usr/local/mysql --with-low-memory

If you have the Sun Workshop 4.2 compiler, you can run configure like this:

CC=cc CFLAGS="-xstrconst -Xa -xO4 -native -mt" CXX=CC CXXFLAGS="-xO4 -native -noex -mt" ./configure --prefix=/usr/local/mysql

shell> CC=cc CFLAGS="-Xa -fast -xO4 -native -xstrconst -mt" \
       CXX=CC CXXFLAGS="-noex -XO4 -mt" \
       ./configure

You may also have to edit the configure script to change this line:

#if !defined(__STDC__) || __STDC__ != 1

to this:

#if !defined(__STDC__)

If you turn on __STDC__ with the -Xc option, the Sun compiler can't compile with the Solaris `pthread.h' header file. This is a Sun bug (broken compiler or broken include file).

If mysqld issues the error message shown below when you run it, you have tried to compile MySQL with the Sun compiler without enabling the multi-thread option (-mt):

libc internal error: _rmutex_unlock: rmutex not held

Add -mt to CFLAGS and CXXFLAGS and try again.

If you get the following error when compiling MySQL with gcc, it means that your gcc is not configured for your version of Solaris!

shell> gcc -O3 -g -O2 -DDBUG_OFF  -o thr_alarm ...
./thr_alarm.c: In function `signal_hand':
./thr_alarm.c:556: too many arguments to function `sigwait'

The proper thing to do in this case is to get the newest version of egcs and compile it with your current gcc compiler! At least for Solaris 2.5, almost all binary versions of gcc have old, unusable include files that will break all programs that use threads (and possibly other programs)!

Solaris doesn't provide static versions of all system libraries (libpthreads and libdl), so you can't compile MySQL with --static. If you try to do so, you will get the error:

ld: fatal: library -ldl: not found

If too many processes try to connect very rapidly to mysqld, you will see this error in the MySQL log:

Error in accept: Protocol error

You might try starting the server with the --set-variable back_log=50 option as a workaround for this.

If you are linking your own MySQL client, you might get the following error when you try to execute it:

ld.so.1: ./my: fatal: libmysqlclient.so.#: open failed: No such file or directory

The problem can be avoided by one of the following methods:

• Link the client with the following flag (instead of -Lpath): -Wl,r/full-path-to-libmysqlclient.so.
• Copy libmysqclient.so to `/usr/lib'.
• Add the pathname of the directory where libmysqlclient.so is located to the LD_RUN_PATH environment variable before running your client.

4.11.2 Solaris 2.7 notes

You can normally use a Solaris 2.6 binary on Solaris 2.7. Most of the Solaris 2.6 issues also apply for Solaris 2.7.

Note that MySQL 3.23.4 and above should be able to autodetect Solaris 2.7 and enable workarounds for the following problems!

Solaris 2.7 has some bugs in the include files. You may see the following error when you use gcc:

/usr/include/widec.h:42: warning: `getwc' redefined
/usr/include/wchar.h:326: warning: this is the location of the previous
definition

If this occurs, you can do the following to fix the problem:

Copy /usr/include/widec.h to .../lib/gcc-lib/os/gcc-version/include and change line 41 from:

#if     !defined(lint) && !defined(__lint)

to

#if     !defined(lint) && !defined(__lint) && !defined(getwc)

Alternatively, you can edit `/usr/include/widec.h' directly. Either way, after you make the fix, you should remove `config.cache' and run configure again!

If you get errors like this when you run make, it's because configure didn't detect the `curses.h' file (probably because of the error in /usr/include/widec.h:

In file included from mysql.cc:50:
/usr/include/term.h:1060: syntax error before `,'
/usr/include/term.h:1081: syntax error before `;'

The solution to this is to do one of the following steps:

• Edit `/usr/include/widec.h' as indicted above and rerun configure
• Remove the #define HAVE_TERM line from `config.h' file and run make again.
• Configure with CFLAGS=-DHAVE_CURSES CXXFLAGS=-DHAVE_CURSES ./configure

4.11.3 Solaris x86 notes

If you are using gcc or egcs on Solaris x86 and you experience problems with core dumps under load, you should use the following configure command:

shell> CC=gcc CFLAGS="-O6 -fomit-frame-pointer" \
       CXX=gcc \
       CXXFLAGS="-O6 -fomit-frame-pointer -felide-constructors -fno-exceptions -fno-rtti" \
       ./configure --prefix=/usr/local/mysql

This will avoid problems with the libstdc++ library and with C++ exceptions.

If this doesn't help, you should compile a debug version and run it with a trace file or under gdb. See section G.1 Debugging a MySQL server.

4.11.4 SunOS 4 notes

On SunOS 4, MIT-pthreads is needed to compile MySQL, which in turn means you will need GNU make.

Some SunOS 4 systems have problems with dynamic libraries and libtool. You can use the following configure line to avoid this problem:

shell> ./configure --disable-shared --with-mysqld-ldflags=-all-static

When compiling readline, you may get warnings about duplicate defines. These may be ignored.

When compiling mysqld, there will be some implicit declaration of function warnings. These may be ignored.

4.11.5 Linux notes (all Linux versions)

MySQL uses LinuxThreads on Linux. If you are using an old Linux version that doesn't have glibc2, you must install LinuxThreads before trying to compile MySQL. http://www.mysql.com/Downloads/Linux

If you can't start mysqld or if mysql_install_db doesn't work, please continue reading! This only happens on Linux system with problems in the LinuxThreads or libc/glibc libraries. There are a lot of simple workarounds to get MySQL to work! The simplest is to use the binary version of MySQL (not the RPM) for Linux x86. One nice aspect of this version is that it's probably 10% faster than any version you would compile yourself! See section 10.3 How compiling and linking affects the speed of MySQL.

One known problem with the binary distribution is that with older Linux systems that use libc (like RedHat 4.x or Slackware), you will get some non-fatal problems with hostname resolution See section 4.6.3.1 Linux notes.

isamchk hangs with libc.so.5.3.12. Upgrading to the newest libc fixes this problem.

When using LinuxThreads you will see a minimum of three processes running. These are in fact threads. There will be one thread for the LinuxThreads manager, one thread to handle connections, and one thread to handle alarms and signals.

If you see a dead mysqld daemon process with ps, this usually means that you have found a bug in MySQL or you have got a corrupted table. See section 18.1 What to do if MySQL keeps crashing.

If you are using LinuxThreads and mysqladmin shutdown doesn't work, you must upgrade to LinuxThreads 0.7.1 or newer.

If you are using RedHat, you might get errors like this:

/usr/bin/perl is needed...
/usr/sh is needed...
/usr/sh is needed...

If so, you should upgrade your version of rpm to `rpm-2.4.11-1.i386.rpm' and `rpm-devel-2.4.11-1.i386.rpm' (or later).

You can get the upgrades of libraries to RedHat 4.2 from ftp://ftp.redhat.com/updates/4.2/i386. Or http://www.sunsite.unc.edu/pub/Linux/distributions/redhat/code/rpm/ for other distributions.

If you are linking your own MySQL client and get the error:

ld.so.1: ./my: fatal: libmysqlclient.so.4: open failed: No such file or directory

when executing them, the problem can be avoided by one of the following methods:

• Link the client with the following flag (instead of -Lpath): -Wl,r/path-libmysqlclient.so.
• Copy libmysqclient.so to `/usr/lib'.
• Add the pathname of the directory where libmysqlclient.so is located to the LD_RUN_PATH environment variable before running your client.

If you are using the Fujitsu compiler (fcc / FCC) you will have some problems compiling MySQL because the Linux header files are very gcc oriented.

The following configure line should work with fcc/FCC:

CC=fcc CFLAGS="-O -K fast -K lib -K omitfp -Kpreex -D_GNU_SOURCE -DCONST=const -DNO_STRTOLL_PROTO" CXX=FCC CXXFLAGS="-O -K fast -K lib  -K omitfp -K preex --no_exceptions --no_rtti -D_GNU_SOURCE -DCONST=const -Dalloca=__builtin_alloca -DNO_STRTOLL_PROTO '-D_EXTERN_INLINE=static __inline'" ./configure --prefix=/usr/local/mysql --enable-assembler --with-mysqld-ldflags=-all-static --disable-shared --with-low-memory

4.11.5.1 Linux-x86 notes

MySQL requires libc version 5.4.12 or newer. It's known to work with libc 5.4.46. glibc version 2.0.6 and later should also work. There have been some problems with the glibc RPMs from RedHat so if you have problems, check whether or not there are any updates! The glibc 2.0.7-19 and 2.0.7-29 RPMs are known to work.

On some older Linux distributions, configure may produce an error like this:

Syntax error in sched.h. Change _P to __P in the /usr/include/sched.h file.
See the Installation chapter in the Reference Manual.

Just do what the error message says and add an extra underscore to the _P macro that has only one underscore, then try again.

You may get some warnings when compiling; those shown below can be ignored:

mysqld.cc -o objs-thread/mysqld.o
mysqld.cc: In function `void init_signals()':
mysqld.cc:315: warning: assignment of negative value `-1' to `long unsigned int'
mysqld.cc: In function `void * signal_hand(void *)':
mysqld.cc:346: warning: assignment of negative value `-1' to `long unsigned int'

In Debian GNU/Linux, if you want MySQL to start automatically when the system boots, do the following:

shell> cp support-files/mysql.server /etc/init.d/mysql.server
shell> /usr/sbin/update-rc.d mysql.server defaults 99

mysql.server can be found in the `share/mysql' directory under the MySQL installation directory, or in the `support-files' directory of the MySQL source tree.

If mysqld always core dumps when it starts up, the problem may be that you have an old `/lib/libc.a'. Try renaming it, then remove `sql/mysqld' and do a new make install and try again. This problem has been reported on some Slackware installations. RedHat 5.0 has also a similar problem with some new glibc versions. See section 4.11.5.2 RedHat 5.0 notes.

If you get the following error when linking mysqld, it means that your `libg++.a' is not installed correctly:

/usr/lib/libc.a(putc.o): In function `_IO_putc':
putc.o(.text+0x0): multiple definition of `_IO_putc'

You can avoid using `libg++.a' by running configure like this:

shell> CXX=gcc ./configure

4.11.5.2 RedHat 5.0 notes

If you have any problems with MySQL on RedHat, you should start by upgrading glibc to the newest possible version!

If you install all the official RedHat patches (including glibc-2.0.7-19 and glibc-devel-2.0.7-19), both the binary and source distributions of MySQL should work without any trouble!

The updates are needed since there is a bug in glibc 2.0.5 in how pthread_key_create variables are freed. With glibc 2.0.5, you must use a statically-linked MySQL binary distribution. If you want to compile from source, you must install the corrected version of LinuxThreads from http://www.mysql.com/Downloads/Linux or upgrade your glibc.

If you have an incorrect version of glibc or LinuxThreads, the symptom is that mysqld crashes after each connection. For example, mysqladmin version will crash mysqld when it finishes!

Another symptom of incorrect libraries is that mysqld crashes at once when it starts. On some Linux systems, this can be fixed by configuring like this:

shell> ./configure --with-mysqld-ldflags=-all-static

On Redhat 5.0, the easy way out is to install the glibc 2.0.7-19 RPM and run configure without the --with-mysqld-ldflags=-all-static option.

For the source distribution of glibc 2.0.7, a patch that is easy to apply and is tested with MySQL may be found at:

http://www.mysql.com/Download/Linux/glibc-2.0.7-total-patch.tar.gz

If you experience crashes like these when you build MySQL, you can always download the newest binary version of MySQL. This is statically-linked to avoid library conflicts and should work on all Linux systems!

MySQL comes with an internal debugger that can generate trace files with a lot of information that can be used to find and solve a wide range of different problems. See section G.1 Debugging a MySQL server.

4.11.5.3 RedHat 5.1 notes

The glibc of RedHat 5.1 (glibc 2.0.7-13) has a memory leak, so to get a stable MySQL version, you must upgrade glibc to 2.0.7-19, downgrade glibc or use a binary version of mysqld. If you don't do this, you will encounter memory problems (out of memory, etc., etc.). The most common error in this case is:

Can't create a new thread (errno 11). If you are not out of available
memory, you can consult the manual for any possible OS dependent bug

After you have upgraded to glibc 2.0.7-19, you can configure MySQL with dynamic linking (the default), but you cannot run configure with the --with-mysqld-ldflags=-all-static option until you have installed glibc 2.0.7-19 from source!

You can check which version of glibc you have with rpm -q glibc.

4.11.5.4 Linux-SPARC notes

In some implementations, readdir_r() is broken. The symptom is that SHOW DATABASES always returns an empty set. This can be fixed by removing HAVE_READDIR_R from `config.h' after configuring and before compiling.

Some problems will require patching your Linux installation. The patch can be found at http://www.mysql.com/patches/Linux-sparc-2.0.30.diff. This patch is against the Linux distribution `sparclinux-2.0.30.tar.gz' that is available at vger.rutgers.edu (a version of Linux that was never merged with the official 2.0.30). You must also install LinuxThreads 0.6 or newer.

Thanks to jacques@solucorp.qc.ca for this information.

4.11.5.5 Linux-Alpha notes

The big problem on Linux-Alpha is that there are still some problems with threads in glibc on this platform. You should start by getting the newest glibc version you can find.

Note that before you run any programs that use threads (like mysqld, thr_alarm or thr_lock), you should raise the shared memory limit (with ulimit). The MySQL benchmarks are known to fail if you forget to do this!

Configure MySQL with the following command:

shell> CC=gcc CCFLAGS="-Dalpha_linux_port" \
       CXX=gcc CXXFLAGS="-O3 -Dalpha_linux_port -felide-constructors -fno-exceptions -fno-rtti" \
       ./configure --prefix=/usr/local/mysql

Try to compile mysys/thr_lock and mysys/thr_alarm. Test that these programs work! (Invoke each one with no arguments. Each should end with test_succeeded if everything was okay.)

After installing MySQL, uncomment the ulimit command in safe_mysqld and add options to increase shared memory.

Note that Linux-Alpha is still an alpha-quality platform for MySQL. With the newest glibc, you have a very good chance of it working.

If you have problems with signals (MySQL dies unexpectedly under high load) you may have found an OS bug with threads and signals. In this case you can tell MySQL not to use signals by configuring with:

shell> CFLAGS=-DDONT_USE_THR_ALARM \
       CXXFLAGS=-DDONT_USE_THR_ALARM \
       ./configure ...

This doesn't affect the performance of MySQL, but has the side effect that you can't kill clients that are "sleeping" on a connection with mysqladmin kill or mysqladmin shutdown. Instead, the client will die when it issues its next command.

4.11.5.6 MkLinux notes

MySQL should work on MkLinux with the newest glibc package (tested with glibc 2.0.7).

4.11.5.7 Qube2 Linux notes

To get MySQL to work on Qube2, (Linux Mips), you need the newest glibc libraries (glibc-2.0.7-29C2 is known to work). You must also use the egcs C++ compiler (egcs-1.0.2-9 or newer).

4.11.6 Alpha-DEC-Unix notes

When compiling threaded programs under Digital UNIX, the documentation recommends using the -pthread option for cc and cxx and the libraries -lmach -lexc (in addition to -lpthread). You should run configure something like this:

shell> CC="cc -pthread" CXX="cxx -pthread -O" \
       ./configure --with-named-thread-libs="-lpthread -lmach -lexc -lc"

When compiling mysqld, you may see a couple of warnings like this:

mysqld.cc: In function void handle_connections()':
mysqld.cc:626: passing long unsigned int *' as argument 3 of
accept(int,sockadddr *, int *)'

You can safely ignore these warnings. They occur because configure can detect only errors, not warnings.

If you start the server directly from the command line, you may have problems with it dying when you log out. (When you log out, your outstanding processes receive a SIGHUP signal.) If so, try starting the server like this:

shell> nohup mysqld [options] &

nohup causes the command following it to ignore any SIGHUP signal sent from the terminal. Alternatively, start the server by running safe_mysqld, which invokes mysqld using nohup for you.

4.11.7 Alpha-DEC-OSF1 notes

If you have problems compiling and have DEC CC and gcc installed, try running configure like this:

shell> CC=cc CFLAGS=-O CXX=gcc CXXFLAGS=-O3 \
       ./configure --prefix=/usr/local/mysql

If you get problems with the `c_asm.h' file, you can create and use a 'dummy' `c_asm.h' file with:

shell> touch include/c_asm.h
shell> CC=gcc CFLAGS=-I./include \
       CXX=gcc CXXFLAGS=-O3 \
       ./configure --prefix=/usr/local/mysql

On OSF1 V4.0D and compiler "DEC C V5.6-071 on Digital UNIX V4.0 (Rev. 878)" the compiler had some strange behavior (undefined asm symbols). /bin/ld also appears to be broken (problems with _exit undefined errors occuring while linking mysqld). On this system, we have managed to compile MySQL with the following configure line, after replacing /bin/ld with the version from OSF 4.0C:

shell> CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql

In some versions of OSF1, the alloca() function is broken. Fix this by removing the line in `config.h' that defines 'HAVE_ALLOCA'.

The alloca() function also may have an incorrect prototype in /usr/include/alloca.h. This warning resulting from this can be ignored.

configure will use the following thread libraries automatically: --with-named-thread-libs="-lpthread -lmach -lexc -lc".

When using gcc, you can also try running configure like this:

shell> CFLAGS=-D_PTHREAD_USE_D4 CXX=gcc CXXFLAGS=-O3 ./configure ....

If you have problems with signals (MySQL dies unexpectedly under high load) you may have found an OS bug with threads and signals. In this case you can tell MySQL not to use signals by configuring with:

shell> CFLAGS=-DDONT_USE_THR_ALARM \
       CXXFLAGS=-DDONT_USE_THR_ALARM \
       ./configure ...

This doesn't affect the performance of MySQL, but has the side effect that you can't kill clients that are "sleeping" on a connection with mysqladmin kill or mysqladmin shutdown. Instead, the client will die when it issues its next command.

4.11.8 SGI-Irix notes

You may have to undefine some things in `config.h' after running configure and before compiling.

In some Irix implementations, the alloca() function is broken. If the mysqld server dies on some SELECT statements, remove the lines from `config.h' that define HAVE_ALLOC and HAVE_ALLOCA_H. If mysqladmin create doesn't work, remove the line from `config.h' that defines HAVE_READDIR_R. You may have to remove the HAVE_TERM_H line as well.

SGI recommends that you install all of the patches on this page as a set: http://support.sgi.com/surfzone/patches/patchset/6.2_indigo.rps.html

At the very minimum, you should install the latest kernel rollup, the latest rld rollup, and the latest libc rollup.

You definately need all the POSIX patches on this page, for pthreads support:

http://support.sgi.com/surfzone/patches/patchset/6.2_posix.rps.html

If you get the something like the following error when compiling `mysql.cc':

"/usr/include/curses.h", line 82: error(1084): invalid combination of type

Then type the following in the top-level directory of your MySQL source tree:

shell> extra/replace bool curses_bool < /usr/include/curses.h > include/curses.h
shell> make

There have also been reports of scheduling problems. If only one thread is running, things go slow. Avoid this by starting another client. This may lead to a 2-to-10-fold increase in execution speed thereafter for the other thread. This is a poorly-understood problem with Irix threads; you may have to improvise to find solutions until this can be fixed.

If you are compiling with gcc, you can use the following configure command:

shell> CC=gcc CXX=gcc CXXFLAGS=-O3 \
       ./configure --prefix=/usr/local/mysql --with-thread-safe-client --with-named-thread-libs=-lpthread

4.11.9 FreeBSD notes

The easiest and therefor the preferred way to install is to use the mysql-server and mysql-client ports available on http://www.freebsd.org

Using these gives you:

• A working MySQL with all optimizations known to work on your version of FreeBSD enabled.
• Automatic configuration and build.
• Startup scripts installed in /usr/local/etc/rc.d
• Ability to see which files that are installed with pkg_info -L. And to remove them all with pkg_delete if you no longer want MySQL on that machine.

It is recomended to use MIT-pthreads on FreeBSD 2.x and native threads on versions 3 and up. It is possible to run with with native threads on some late 2.2.x versions but you may encounter problems shutting down mysqld.

Be sure to have your name resolver setup correct. Otherwise you may experience resolver delays or failures when connecting to mysqld.

Make sure that the localhost entry in the `/etc/hosts' file is correct (otherwise you will have problems connecting to the database). The `/etc/hosts' file should start with a line:

127.0.0.1       localhost localhost.your.domain

If you notice that configure will use MIT-pthreads, you should read the MIT-pthreads notes. See section 4.9 MIT-pthreads notes.

If you get an error from make install that it can't find `/usr/include/pthreads', configure didn't detect that you need MIT-pthreads. This is fixed by executing these commands:

shell> rm config.cache
shell> ./configure --with-mit-threads

The behavior of FreeBSD make is slightly different from that of GNU make. If you have make-related problems, you should install GNU make.

FreeBSD is also known to have a very low default file handle limit. See section 18.11 File not found. Uncomment the ulimit -n section in safe_mysqld or raise the limits for the mysqld user in /etc/login.conf (and rebuild it witg cap_mkdb /etc/login.conf) also be sure you set the appropriate Class for this user in the password file if you are not using the default (use: chpass mysqld-user-name)

If you have a problem with SELECT NOW() returning values in GMT and not your local time, you have to set the TZ environment variable to your current timezone. This should be done for the environment in which the server runs, for example, in safe_mysqld or mysql.server.

To get a secure and stable system you should only use FreeBSD kernels that are marked -STABLE

4.11.10 NetBSD notes

To compile on NetBSD you need GNU make. Otherwise the compile will crash when make tries to run lint on C++ files.

4.11.11 BSD/OS notes

4.11.11.1 BSD/OS 2.x notes

If you get the following error when compiling MySQL, your ulimit value for virtual memory is too low:

item_func.h: In method `Item_func_ge::Item_func_ge(const Item_func_ge &)':
item_func.h:28: virtual memory exhausted
make[2]: *** [item_func.o] Error 1

Try using ulimit -v 80000 and run make again. If this doesn't work and you are using bash, try switching to csh or sh; some BSDI users have reported problems with bash and ulimit.

If you are using gcc, you may also use have to use the --with-low-memory flag for configure to be able to compile `sql_yacc.cc'.

If you have a problem with SELECT NOW() returning values in GMT and not your local time, you have to set the TZ environment variable to your current timezone. This should be done for the environment in which the server runs, for example in safe_mysqld or mysql.server.

4.11.11.2 BSD/OS 3.x notes

Upgrade to BSD/OS 3.1. If that is not possible, install BSDIpatch M300-038.

Use the following command when configuring MySQL:

shell> env CXX=shlicc++ CC=shlicc2 \
       ./configure \
           --prefix=/usr/local/mysql \
           --localstatedir=/var/mysql \
           --without-perl \
           --with-unix-socket-path=/var/mysql/mysql.sock

The following is also known to work:

shell> env CC=gcc CXX=gcc CXXFLAGS=-O3 \
       ./configure \
           --prefix=/usr/local/mysql \
           --with-unix-socket-path=/var/mysql/mysql.sock

You can change the directory locations if you wish, or just use the defaults by not specifying any locations.

If you have problems with performance under heavy load, try using the --skip-thread-priority option to safe_mysqld! This will run all threads with the same priority; on BSDI 3.1, this gives better performance (at least until BSDI fixes their thread scheduler).

If you get the error virtual memory exhausted while compiling, you should try using ulimit -v 80000 and run make again. If this doesn't work and you are using bash, try switching to csh or sh; some BSDI users have reported problems with bash and ulimit.

4.11.11.3 BSD/OS 4.x notes

BSDI 4.x has some thread related bugs. If you want to use MySQL on this, you should install all thread related patches. At least M400-023 should be installed.

4.11.12 SCO notes

The current port is tested only on a "sco3.2v5.0.4" and "sco3.2v5.0.5" system. There has also been a lot of progress on a port to "sco 3.2v4.2".

1. For OpenServer 5.0.X you need to use GDS in Skunkware 95 (95q4c). This is necessary because GNU gcc 2.7.2 in Skunkware 97 does not have GNU as. You can also use egcs 1.1.2 or newer http://www.egcs.com/. If you are using egcs 1.1.2 you have to execute the following command:

   shell> cp -p /usr/include/pthread/stdtypes.h /usr/local/lib/gcc-lib/i386-pc-sco3.2v5.0.5/egcs-2.91.66/include/pthread/
   

2. You need the port of GCC 2.5.? for this product and the Development system. They are required on this version of SCO UNIX. You cannot just use the GCC Dev system.
3. You should get the FSU Pthreads package and install it first. This can be found at http://www.cs.wustl.edu/~schmidt/ACE_wrappers/FSU-threads.tar.gz. You can also get a precompiled package from ftp://www.mysql.com/pub/mysql/Downloads/SCO/FSU-threads-3.5c.tar.gz.
4. FSU Pthreads can be compiled with SCO UNIX 4.2 with tcpip. Or OpenServer 3.0 or Open Desktop 3.0 (OS 3.0 ODT 3.0), with the SCO Development System installed using a good port of GCC 2.5.X ODT or OS 3.0 you will need a good port of GCC 2.5.? There are a lot of problems without a good port. The port for this product requires the SCO UNIX Development system. Without it, you are missing the libraries and the linker that is needed.
5. To build FSU Pthreads on your system, do the following:
   1. Run ./configure in the `threads/src' directory and select the SCO OpenServer option. This command copies `Makefile.SCO5' to `Makefile'.
   2. Run make.
   3. To install in the default `/usr/include' directory, login as root, then cd to the `thread/src' directory, and run make install.
6. Remember to use GNU make when making MySQL.
7. On OSR 5.0.5, you should use the following configure line:

   shell> CC="gcc -DSCO" CXX="gcc -DSCO" ./configure
   

   The -DSCO is needed to help configure detect some thread functions properly. If you forget -DSCO, you will get the following error message while compiling:

   my_pthread.c: In function `my_pthread_mutex_init':
   my_pthread.c:374: `pthread_mutexattr_default' undeclared (first use this function)
   

8. If you don't start safe_mysqld as root, you probably will get only the default 110 open files per process. mysqld will write a note about this in the log file.
9. With SCO 3.2V5.0.5, you should use a FSU Pthreads version 3.5c or newer. The following configure command should work:

   shell> CC="gcc -belf" ./configure --prefix=/usr/local/mysql --disable-shared
   

10. With SCO 3.2V4.2, you should use a FSU Pthreads version 3.5c or newer. The following configure command should work:

    shell> CFLAGS="-D_XOPEN_XPG4" CXX=gcc CXXFLAGS="-D_XOPEN_XPG4" \
           ./configure \
               --with-debug --prefix=/usr/local/mysql \
               --with-named-thread-libs="-lgthreads -lsocket -lgen -lgthreads" \
               --with-named-curses-libs="-lcurses"
    

    You may get some problems with some include files. In this case, you can find new SCO-specific include files at ftp://www.mysql.com/pub/mysql/Downloads/SCO/SCO-3.2v4.2-includes.tar.gz. You should unpack this file in the `include' directory of your MySQL source tree.

SCO development notes:

• MySQL should automatically detect FSU Pthreads and link mysqld with -lgthreads -lsocket -lgthreads.
• The SCO development libraries are reentrant in FSU Pthreads. SCO claims that its libraries' functions are reentrant, so they must be reentrant with FSU Pthreads. FSU Pthreads on OpenServer tries to use the SCO scheme to make reentrant library.
• FSU Pthreads (at least the version at www.mysql.com) comes linked with GNU malloc. If you encounter problems with memory usage, make sure that `gmalloc.o' is included in `libgthreads.a' and `libgthreads.so'.
• In FSU Pthreads, the following system calls are pthreads-aware: read(), write(), getmsg(), connect(), accept(), select() and wait().

If you want to install DBI on SCO, you have to edit the `Makefiles' in DBI-xxx and each subdirectory:

OLD:                                  NEW:
CC = cc                               CC = gcc -belf
CCCDLFLAGS = -KPIC -W1,-Bexport       CCCDLFLAGS = -fpic
CCDLFLAGS = -wl,-Bexport              CCDLFLAGS =

LD = ld                               LD = gcc -belf -G -fpic
LDDLFLAGS = -G -L/usr/local/lib       LDDLFLAGS = -L/usr/local/lib
LDFLAGS = -belf -L/usr/local/lib      LDFLAGS = -L/usr/local/lib

LD = ld                               LD = gcc -belf -G -fpic
OPTIMISE = -Od         		      OPTIMISE = -O1

OLD:
CCCFLAGS = -belf -dy -w0 -U M_XENIX -DPERL_SCO5 -I/usr/local/include

NEW:
CCFLAGS = -U M_XENIX -DPERL_SCO5 -I/usr/local/include

This is because the Perl dynaloader will not load the DBI modules if they were compiled with icc or cc.

Perl works best when compiled with cc.

4.11.13 SCO Unixware 7.0 notes

You must use a version of MySQL at least as recent as 3.22.13, since that version fixes some portability problems under Unixware.

We have been able to compile MySQL with the following configure command on UnixWare 7.0.1:

shell> CC=cc CXX=CC ./configure --prefix=/usr/local/mysql

4.11.14 IBM-AIX notes

Automatic detection of xlC is missing from Autoconf, so a configure command something like this is needed when using the IBM compiler:

shell> CC="xlc_r -ma -O3 -qstrict -DHAVE_INT_8_16_32" \
       CXX="xlC_r -ma -O3 -qstrict -DHAVE_INT_8_16_32" \
       ./configure

If you are using egcs to compile MySQL, you MUST use the -fno-exceptions flag, as the exception handling in egcs is not thread-safe! (This is tested with egcs 1.1.) We recommend the following configure line with egcs and gcc on AIX:

shell> CXX=gcc \
       CXXFLAGS="-felide-constructors -fno-exceptions -fno-rtti" \
       ./configure --prefix=/home/monty --with-debug --with-low-memory

If you have problems with signals (MySQL dies unexpectedly under high load) you may have found an OS bug with threads and signals. In this case you can tell MySQL not to use signals by configuring with:

shell> CFLAGS=-DDONT_USE_THR_ALARM CXX=gcc \
       CXXFLAGS="-felide-constructors -fno-exceptions -fno-rtti -DDONT_USE_THR_ALARM" \
       ./configure --prefix=/home/monty --with-debug --with-low-memory

This doesn't affect the performance of MySQL, but has the side effect that you can't kill clients that are "sleeping" on a connection with mysqladmin kill or mysqladmin shutdown. Instead, the client will die when it issues its next command.

4.11.15 HP-UX notes

There are a couple of "small" problems when compiling MySQL on HP-UX. We recommend that you use gcc instead of the HP-UX native compiler, because gcc produces better code!

We recommend one to use gcc 2.95 on HP-UX. Don't use high optimization flags (like -O6) as this may not be safe on HP-UX.

Note that MIT-pthreads can't be compiled with the HP-UX compiler, because it can't compile .S (assembler) files.

The following configure line should work:

CFLAGS="-DHPUX -I/opt/dce/include" CXXFLAGS="-DHPUX -I/opt/dce/include -felide-constructors -fno-exceptions -fno-rtti" CXX=gcc ./configure --with-pthread --with-named-thread-libs='-ldce' --prefix=/usr/local/mysql --disable-shared

If you are compiling gcc 2.95 yourself, you should NOT link it with the DCE libraries (libdce.a or libcma.a) if you want to compile MySQL with MIT-pthreads. If you mix the DCE and MIT-pthreads packages you will get a mysqld to which you cannot connect. Remove the DCE libraries while you compile gcc 2.95!

4.12 Win32 notes

This section describes installation and use of MySQL on Win32. This is also described in the `README' file that comes with the MySQL Win32 distribution.

4.12.1 Installing MySQL on Win32

If you don't have a registered version of MySQL, you should first download the shareware version from:

MySQL 3.21.29

If you plan to connect to MySQL from some other program, you will probably also need the MyODBC driver. You can find this at the MySQL download page.

To install either distribution, unzip it in some empty directory and run the Setup.exe program.

Installation takes place in `C:\mysql'.

4.12.2 Starting MySQL on Win95 / Win98

MySQL uses TCP/IP to connect a client to a server. (This will allow any machine on your network to connect to your MySQL server). Because of this, you must install TCP/IP on your machine before starting MySQL. You can find TCP/IP on your Windows CD-ROM.

Note that if you are using an old Win95 release (for example OSR2), it's likely that you have an old Winsock package! MySQL requires Winsock 2! You can get the newest Winsock from Microsoft. Win98 has as default the new Winsock 2 library, so the above doesn't apply for Win98.

There are 2 different MySQL servers you can use:

Both of the above should work on any Intel processor >= i386.

To start the mysqld server, you should start a MS-DOS window and type:

C:\mysql\bin\mysqld

This will start mysqld in the background without a window.

You can kill the MySQL server by executing:

C:\mysql\bin\mysqladmin -u root shutdown

Note that Win95/Win98 don't support creation of named pipes. On Win95/Win98, you can only use named pipes to connect to a remote MySQL running on an NT server.

4.12.3 Starting MySQL on NT

The Win95/Win98 section also applies to MySQL on NT, with the following differences:

To get MySQL to work with TCP/IP, you must install service pack 3 (or newer)!

For NT, the server name is mysqld-nt. Normally you should install MySQL as a service on NT:

C:\mysql\bin\mysqld-nt --install

(You could use the mysqld or mysqld-opt servers on NT, but those cannot be started as a service or use named pipes.)

You can start and stop the MySQL service with:

NET START mysql
NET STOP mysql

Note that in this case you can't use any other options for mysqld-nt!

You can also run mysqld-nt as a standalone program on NT if you need to start mysqld-nt with any options! If you start mysqld-nt without options on NT, mysqld-nt tries to starts itself as a service with the default service options. If you have stopped mysqld-nt, you have to start it with NET START mysql.

The service is installed with the name MySql. Once installed, it must be started using Services Control Manager (SCM) Utility (found in Control Panel) or by using the NET START MySQL command. If any options are desired, they must be specified as "Startup parameters" in the SCM utility before you start the MySQL service. Once running, mysqld-nt can be stopped using mysqladmin or from the SCM utility or by using the command NET STOP MySQL. If you use SCM to stop mysqld-nt, there is a strange message from SCM about mysqld shutdown normally. When run as a service, mysqld-nt has no access to a console and so no messages can be seen.

On NT you can get the following service error messages:

If you have problems installing mysqld-nt as a service, try starting it with the full path:

C:\mysql\bin\mysqld --install

If this doesn't work, you can get mysqld-nt to start properly by fixing the path in the registry!

If you don't want to start mysqld-nt as a service, you can start it as follows:

C:\mysql\bin\mysqld-nt --standalone

or

C:\mysql\bin\mysqld-nt --standalone --debug

The last version gives you a debug trace in `C:\mysqld.trace'.

4.12.4 Running MySQL on Win32

MySQL supports TCP/IP on all Win32 platforms and named pipes on NT. The default is to use named pipes for local connections on NT and TCP/IP for all other cases if the client has TCP/IP installed. The host name specifies which protocol is used:

You can force a MySQL client to use named pipes by specifying the --pipe option. Use the --socket option to specify the name of the pipe.

You can test whether or not MySQL is working by executing the following commands:

C:\mysql\bin\mysqlshow
C:\mysql\bin\mysqlshow -u root mysql
C:\mysql\bin\mysqladmin version status proc
C:\mysql\bin\mysql test

By default, MySQL-Win32 is configured to be installed in `C:\mysql'. If you want to install MySQL elsewhere, install it in `C:\mysql', then move the installation to where you want it. If you do move MySQL, you must tell mysqld where everything is by supplying options to mysqld. Use C:\mysql\bin\mysqld --help to display all options! For example, if you have moved the MySQL distribution to `D:\programs\mysql', you must start mysqld with: D:\programs\mysql\bin\mysqld --basedir D:\programs\mysql

With the registered version of MySQL, you can also create a `C:\my.cnf' file that holds any default options for the MySQL server. Copy the file `\mysql\my-example.cnf' to `C:\my.cnf' and edit this to suit your setup. Note that you should specify all paths with / instead of \. If you use \, you need to specify this twice, as \ is the escape character in MySQL. See section 4.15.4 Option files.

If mysqld is slow to answer to connections on Win95/Win98, there is probably a problem with your DNS. In this case, start mysqld with --skip-name-resolve and use only localhost and IP numbers in the MySQL grant tables. You can also avoid DNS when connecting to a mysqld-nt MySQL server running on NT by using the --pipe argument to specify use of named pipes. This works for most MySQL clients.

There are two versions of the MySQL command line tool:

mysql	Compiled on native Win32, which offers very limited text editing capabilities.
mysqlc	Compiled with the Cygnus GNU compiler and libraries, which offers readline editing.

If you want to use mysqlc.exe, you must copy `C:\mysql\lib\cygwinb19.dll' to `\windows\system' (or similar place).

The default privileges on Win32 give all local users full privileges to all databases. To make MySQL more secure, you should set a password for all users and remove the row in the mysql.user table that has Host='localhost' and User=".

You should also add a password for the root user:

C:\mysql\bin\mysql mysql
mysql> DELETE FROM user WHERE Host='localhost' AND User=";
mysql> QUIT
C:\mysql\bin\mysqladmin reload
C:\mysql\bin\mysqladmin -u root password your_password

After you've set the password, if you want to take down the mysqld server, you can do so using this command:

mysqladmin --user=root --password=your_password shutdown

4.12.5 Connecting to a remote MySQL from Win32 with SSH

Here is a note about how to connect to get a secure connection to remote MySQL server with SSH (by David Carlson).

• Install SSH client on your windows machine - I used a free SSH client from http://www.doc.ic.ac.uk/~ci2/ssh/. Other useful links: http://www.npaci.edu/Security/npaci_security_software.html and http://www.npaci.edu/Security/samples/ssh32_windows/index.html.
• Start SSH. Set Host Name = yourmysqlserver name or IP address. Set userid=your userid to log in to your server
• Click on "local forwards". Set local port: 3306, host: localhost, remote port: 3306
• Save everything, otherwise you'll have to redo it the next time.
• Log in to your server with SSH.
• Start some ODBC application (for example Access)
• Create a new file and link to mySQL using the ODBC driver the same way you normally do except for server, user "localhost".

That's it. It works very well with a direct Internet connection. I'm having problems with SSH conflicting with my Win95 network and Wingate - but that'll be the topic of a posting on another software company's usegroup!

4.12.6 MySQL-Win32 compared to Unix MySQL

MySQL-Win32 has by now proven itself to be very stable. This version of MySQL has the same features as the corresponding Unix version with the following exceptions:

Win95 and threads

Win95 leaks about 200 bytes of main memory for each thread creation. Because of this, you shouldn't run mysqld for an extended time on Win95 if you do many connections, since each connection in MySQL creates a new thread! WinNT and Win98 don't suffer from this bug.

Blocking read

MySQL uses a blocking read for each connection. This means that:

• A connection will not be disconnected automatically after 8 hours, as happens with the Unix version of MySQL.
• If a connection "hangs," it's impossible to break it without killing MySQL.
• mysqladmin kill will not work on a sleeping connection.
• mysqladmin shutdown can't abort as long as there are sleeping connections.

We plan to fix this in the near future.

UDF functions

For the moment, MySQL-Win32 does not support user definable functions.

DROP DATABASE

You can't drop a database that is in use by some thread.

Killing MySQL from the task manager

You can't kill MySQL from the task manager or with the shutdown utility in Windows95. You must take it down with mysqladmin shutdown.

Case-insensitive names

Filenames are case insensitive on Win32, so database and table names are also case insensitive in MySQL for Win32. The only restriction is that database and table names must be given in the same case throughout a given statement. The following query would not work because it refers to a table both as my_table and as MY_TABLE:

SELECT * FROM my_table WHERE MY_TABLE.col=1;

The `\' directory character

Pathname components in Win95 are separated by `\' characters, which is also the escape character in MySQL. If you are using LOAD DATA INFILE or SELECT ... INTO OUTFILE, you must double the `\' character or use Unix style filenames `/' characters:

LOAD DATA INFILE "C:\\tmp\\skr.txt" INTO TABLE skr;
SELECT * FROM skr INTO OUTFILE 'C:/tmp/skr.txt';

Can't open named pipe error

If you use the shareware version of MySQL-Win32 on NT with the newest mysql-clients you will get the following error:

error 2017: can't open named pipe to host: . pipe...

This is because the release version of MySQL uses named pipes on NT by default. You can avoid this error by using the --host=localhost option to the new MySQL clients or create a file `C:\my.cnf' that contains the following information:

[client]
host = localhost

Access denied for user error

If you get the error Access denied for user: 'some-user@unknown' to database 'mysql' when accessing a MySQL server on the same machine, this means that MySQL can't resolve your host name properly. To fix this, you should create a file `\windows\hosts' with the following information:

127.0.0.1       localhost

Here are some open issues for anyone who might want to help us with the Win32 release:

• Make a single user MYSQL.DLL server. This should include everything in a standard MySQL server, except thread creation. This will make MySQL much easier to use in applications that don't need a true client/server and don't need to access the server from other hosts.
• Add some nice "start" and "shutdown" icons to the MySQL installation.
• Create a tool to manage registry entries for the MySQL startup options. The registry entry reading is already coded into mysqld.cc, but it should be recoded to be more "parameter" oriented. The tool should also be able to update the `\my.cnf' file if the user would prefer to use this instead of the registry.
• When registering mysqld as a service with --install (on NT) it would be nice if you could also add default options on the command line. For the moment, the workaround is to update the `C:\my.cnf' file instead.
• When you suspend a laptop running Win95, the mysqld daemon doesn't accept new connections when the laptop is resumed. We don't know if this is a problem with Win95, TCP/IP or MySQL.
• It would be real nice to be able to kill mysqld from the task manager. For the moment, you must use mysqladmin shutdown.
• Port readline to Win32 for use in the mysql command line tool.
• GUI versions of the standard MySQL clients (mysql, mysqlshow, mysqladmin, and mysqldump) would be nice.
• It would be nice if the socket "read" and "write" functions in `net.c' were interruptible. This would make it possible to kill open threads with mysqladmin kill on Win32.
• Documentation of which Windows programs work with MySQL-Win32/MyODBC and what must be done to get them working.
• mysqld always starts in the "C" locale and not in the default locale. We would like to have mysqld use the current locale for the sort order.
• Port sqlclient to Win32 (almost done) and add more features to it!
• Add more options to MysqlManager.
• Change the communication protocol between the server and client to use Windows internal communication instead of sockets and TCP/IP.
• Implement UDF functions with .DLLs.
• Add macros to use the faster thread-safe increment/decrement methods provided by Win32.

Other Win32-specific issues are described in the `README' file that comes with the MySQL-Win32 distribution.

4.13 OS/2 notes

MySQL uses quite a few open files. Because of this, you should add something like the following to your `CONFIG.SYS' file:

SET EMXOPT=-c -n -h1024

If you don't do this, you will probably run into the following error:

File 'xxxx' not found (Errcode: 24)

When using MySQL with OS/2 Warp 3, FixPack 29 or above is required. With OS/2 Warp 4, FixPack 4 or above is required. This is a requirement of the Pthreads library. MySQL must be installed in a partition that supports long file names such as HPFS, FAT32, etc.

The `INSTALL.CMD' script must be run from OS/2's own `CMD.EXE' and may not work with replacement shells such as `4OS2.EXE'.

The `scripts/mysql-install-db' script has been renamed: it is now called `install.cmd' and is a REXX script which will set up the default MySQL security settings and create the WorkPlace Shell icons for MySQL.

Dynamic module support is compiled in but not fully tested. Dynamic modules should be compiled using the Pthreads runtime library.

gcc -Zdll -Zmt -Zcrtdll=pthrdrtl -I../include -I../regex -I.. \
    -o example udf_example.cc -L../lib -lmysqlclient udf_example.def
mv example.dll example.udf

Note: Due to limitations in OS/2, UDF module name stems must not exceed 8 characters. Modules are stored in the `/mysql2/udf' directory; the safe-mysqld.cmd script will put this directory in the BEGINLIBPATH environment variable. When using UDF modules, specified extensions are ignored -- it is assumed to be `.udf'. For example, in Unix, the shared module might be named `example.so' and you would load a function from it like this:

CREATE FUNCTION metaphon RETURNS STRING SONAME "example.so";

Is OS/2, the module would be named `example.udf', but you would not specify the module extension:

CREATE FUNCTION metaphon RETURNS STRING SONAME "example";

4.14 TcX binaries

As a service, TcX provides a set of binary distributions of MySQL that are compiled at TcX or at sites where customers kindly have given us access to their machines.

These distributions are generated with scripts/make_binary_distribution and are configured with the following compilers and options:

SunOS 4.1.4 2 sun4c with gcc 2.7.2.1

CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql --disable-shared

SunOS 5.5.1 sun4u with egcs 1.0.3a

CC=gcc CFLAGS="-O6 -fomit-frame-pointer" CXX=gcc CXXFLAGS="-O6 -fomit-frame-pointer -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --with-low-memory

SunOS 5.6 sun4u with egcs 2.90.27

CC=gcc CFLAGS="-O6 -fomit-frame-pointer" CXX=gcc CXXFLAGS="-O6 -fomit-frame-pointer -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --with-low-memory

SunOS 5.6 i86pc with gcc 2.8.1

CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql --with-low-memory

Linux 2.0.33 i386 with pgcc 2.90.29 (egcs 1.0.3a)

CFLAGS="-O6 -mpentium -mstack-align-double -fomit-frame-pointer" CXX=gcc CXXFLAGS="-O6 -mpentium -mstack-align-double -fomit-frame-pointer -felide-constructors -fno-exceptions -fno-rtti" ./configure --prefix=/usr/local/mysql --enable-assembler --with-mysqld-ldflags=-all-static

SCO 3.2v5.0.4 i386 with gcc 2.7-95q4

CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql

AIX 2 4 with gcc 2.7.2.2

CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql

OSF1 V4.0 564 alpha with gcc 2.8.1

CC=gcc CFLAGS=-O CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql --with-low-memory

Irix 6.3 IP32 with gcc 2.8.0

CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql

BSDI BSD/OS 3.1 i386 with gcc 2.7.2.1

CC=gcc CXX=gcc CXXFLAGS=-O ./configure --prefix=/usr/local/mysql

BSDI BSD/OS 2.1 i386 with gcc 2.7.2

CC=gcc CXX=gcc CXXFLAGS=-O3 ./configure --prefix=/usr/local/mysql

Anyone who has more optimal options for any of the configurations listed above can always mail them to the developer's mailing list at

RPM distributions prior to MySQL 3.22 are user-contributed. Beginning with 3.22, some RPMs are TcX-generated.

4.15 Post-installation setup and testing

Once you've installed MySQL (from either a binary or source distribution), you need to initialize the grant tables, start the server and make sure that the server works okay. You may also wish to arrange for the server to be started and stopped automatically when your system starts up and shuts down.

Normally you install the grant tables and start the server like this for installation from a source distribution:

shell> ./scripts/mysql_install_db
shell> cd mysql_installation_directory
shell> ./bin/safe_mysqld &

For a binary distribution, do this:

shell> cd mysql_installation_directory
shell> ./bin/mysql_install_db
shell> ./bin/safe_mysqld &

Testing is most easily done from the top-level directory of the MySQL distribution. For a binary distribution, this is your installation directory (typically something like `/usr/local/mysql'). For a source distribution, this is the main directory of your MySQL source tree.

In the commands shown below in this section and in the following subsections, BINDIR is the path to the location in which programs like mysqladmin and safe_mysqld are installed. For a binary distribution, this is the `bin' directory within the distribution. For a source distribution, BINDIR is probably `/usr/local/bin', unless you specified an installation directory other than `/usr/local' when you ran configure. EXECDIR is the location in which the mysqld server is installed. For a binary distribution, this is the same as BINDIR. For a source distribution, EXECDIR is probably `/usr/local/libexec'.

Testing is described in detail below:

1. If necessary, start the mysqld server and set up the initial MySQL grant tables containing the privileges that determine how users are allowed to connect to the server. This is normally done with the mysql_install_db script:

   shell> scripts/mysql_install_db
   

   Typically, mysql_install_db needs to be run only the first time you install MySQL. Therefore, if you are upgrading an existing installation, you can skip this step. (However, mysql_install_db is quite safe to use and will not update any tables that already exist, so if you are unsure what to do, you can always run mysql_install_db.) mysql_install_db creates six tables (user, db, host, tables_priv, columns_priv and func) in the mysql database. A description of the initial privileges is given in section 6.10 Setting up the initial MySQL privileges. Briefly, these privileges allow the MySQL root user to do anything, and allow anybody to create or use databases with a name of 'test' or starting with 'test_'. If you don't set up the grant tables, the following error will appear in the log file when you start the server:

   mysqld: Can't find file: 'host.frm'
   

   The above may also happens with a binary MySQL distribution if you don't start MySQL by executing exactly ./bin/safe_mysqld! You might need to run mysql_install_db as root. However, if you prefer, you can run the MySQL server as an unprivileged (non-root) user, provided that user can read and write files in the database directory. Instructions for running MySQL as an unprivileged user are given in section 18.8 How to run MySQL as a normal user. If you have problems with mysql_install_db, see section 4.15.1 Problems running mysql_install_db. There are some alternatives to running the mysql_install_db script as it is provided in the MySQL distribution:
   • You may want to edit mysql_install_db before running it, to change the initial privileges that are installed into the grant tables. This is useful if you want to install MySQL on a lot of machines with the same privileges. In this case you probably should need only to add a few extra INSERT statements to the mysql.user and mysql.db tables!
   • If you want to change things in the grant tables after installing them, you can run mysql_install_db, then use mysql -u root mysql to connect to the grant tables as the MySQL root user and issue SQL statements to modify the grant tables directly.
   • It is possible to recreate the grant tables completely after they have already been created. You might want to do this if you've already installed the tables but then want to recreate them after editing mysql_install_db.
   For more information about these alternatives, see section 6.10 Setting up the initial MySQL privileges.
2. Start the MySQL server like this:

   shell> cd mysql_installation_directory
   shell> bin/safe_mysqld &
   

   If you have problems starting the server, see section 4.15.2 Problems starting the MySQL server.
3. Use mysqladmin to verify that the server is running. The following commands provide a simple test to check that the server is up and responding to connections:

   shell> BINDIR/mysqladmin version
   shell> BINDIR/mysqladmin variables
   

   The output from mysqladmin version varies slightly depending on your platform and version of MySQL, but should be similar to that shown below:

   shell> BINDIR/mysqladmin version
   mysqladmin  Ver 6.3 Distrib 3.22.9-beta, for pc-linux-gnu on i686
   TCX Datakonsult AB, by Monty
   
   Server version          3.22.9-beta
   Protocol version        10
   Connection              Localhost via UNIX socket
   TCP port                3306
   UNIX socket             /tmp/mysql.sock
   Uptime:                 16 sec
   
   Running threads: 1  Questions: 20  Reloads: 2  Open tables: 3
   

   To get a feeling for what else you can do with BINDIR/mysqladmin, invoke it with the --help option.
4. Verify that you can shut down the server:

   shell> BINDIR/mysqladmin -u root shutdown
   

5. Verify that you can restart the server. Do this using safe_mysqld or by invoking mysqld directly. For example:

   shell> BINDIR/safe_mysqld --log &
   

   If safe_mysqld fails, try running it from the MySQL installation directory (if you are not already there). If that doesn't work, see section 4.15.2 Problems starting the MySQL server.
6. Run some simple tests to verify that the server is working. The output should be similar to what is shown below:

   shell> BINDIR/mysqlshow
   +-----------+
   | Databases |
   +-----------+
   | mysql     |
   +-----------+
   
   shell> BINDIR/mysqlshow mysql
   Database: mysql
   +--------------+
   |    Tables    |
   +--------------+
   | columns_priv |
   | db           |
   | func         |
   | host         |
   | tables_priv  |
   | user         |
   +--------------+
   
   shell> BINDIR/mysql -e "select host,db,user from db" mysql
   +------+--------+------+
   | host | db     | user |
   +------+--------+------+
   | %    | test   |      |
   | %    | test_% |      |
   +------+--------+------+
   

   There is also a benchmark suite in the `sql-bench' directory (under the MySQL installation directory) that you can use to compare how MySQL performs on different platforms. The `sql-bench/Results' directory contains the results from many runs against different databases and platforms. To run all tests, execute these commands:

   shell> cd sql-bench
   shell> run-all-tests
   

   If you don't have the `sql-bench' directory, you are probably using an RPM for a binary distribution. (Source distribution RPMs include the benchmark directory.) In this case, you must first install the benchmark suite before you can use it. Beginning with MySQL 3.22, there are benchmark RPM files named `mysql-bench-VERSION-i386.rpm' that contain benchmark code and data. If you have a source distribution, you can also run the tests in the `tests' subdirectory. For example, to run `auto_increment.tst', do this:

   shell> BINDIR/mysql -vvf test < ./tests/auto_increment.tst
   

   The expected results are shown in the `./tests/auto_increment.res' file.

4.15.1 Problems running mysql_install_db

This section lists problems you might encounter when you run mysql_install_db:

mysql_install_db doesn't install the grant tables

You may find that mysql_install_db fails to install the grant tables and terminates after displaying the following messages:

starting mysqld daemon with databases from XXXXXX
mysql daemon ended

In this case, you should examine the log file very carefully! The log should be located in the directory `XXXXXX' named by the error message, and should indicate why mysqld didn't start. If you don't understand what happened, include the log when you post a bug report using mysqlbug! See section 2.3 How to report bugs or problems.

There is already a mysqld daemon running

In this case, you have probably don't have to run mysql_install_db at all. You have to run mysql_install_db only once, when you install MySQL the first time.

Installing a second mysqld daemon doesn't work when one daemon is running

This can happen when you already have an existing MySQL installation, but want to put a new installation in a different place (e.g., for testing, or perhaps you simply want to run two installations at the same time). Generally the problem that occurs when you try to run the second server is that it tries to use the same socket and port as the old one. In this case you will get the error message: Can't start server: Bind on TCP/IP port: Address already in use or Can't start server : Bind on unix socket... You can start the new server with a different socket and port as follows:

shell> MYSQL_UNIX_PORT=/tmp/mysqld-new.sock
shell> MYSQL_TCP_PORT=3307
shell> export MYSQL_UNIX_PORT MYSQL_TCP_PORT
shell> scripts/mysql_install_db
shell> bin/safe_mysqld &

After this, you should edit your server boot script to start both daemons with different sockets and ports. For example, it could invoke safe_mysqld twice, but with different --socket, --port and --basedir options for each invocation.

You don't have write access to `/tmp'

If you don't have write access to create a socket file at the default place (in `/tmp') or permission to create temporary files in `/tmp,' you will get an error when running mysql_install_db or when starting or using mysqld. You can specify a different socket and temporary directory as follows:

shell> TMPDIR=/some_tmp_dir/
shell> MYSQL_UNIX_PORT=/some_tmp_dir/mysqld.sock
shell> export TMPDIR MYSQL_UNIX_PORT

`some_tmp_dir' should be the path to some directory for which you have write permission. After this you should be able to run mysql_install_db and start the server with these commands:

shell> scripts/mysql_install_db
shell> BINDIR/safe_mysqld &

mysqld crashes immediately

If you are running RedHat 5.0 with a version of glibc older than 2.0.7-5, you should make sure you have installed all glibc patches! There is a lot of information about this in the MySQL mail archives. Links to the mail archives are available at the online MySQL documentation page. Also, see section 4.11.5 Linux notes (all Linux versions). You can also start mysqld manually using the --skip-grant option and add the privilege information yourself using mysql:

shell> BINDIR/safe_mysqld --skip-grant &
shell> BINDIR/mysql -u root mysql

From mysql, manually execute the SQL commands in mysql_install_db. Make sure you run mysqladmin reload afterward to tell the server to reload the grant tables.

4.15.2 Problems starting the MySQL server

Generally, you start the mysqld server in one of three ways:

• By invoking mysql.server. This script is used primarily at system startup and shutdown, and is described more fully in section 4.15.3 Starting and stopping MySQL automatically.
• By invoking safe_mysqld, which tries to determine the proper options for mysqld and then runs it with those options.
• By invoking mysqld directly.

Whichever method you use to start the server, if it fails to start up correctly, check the log file to see if you can find out why. Log files are located in the data directory (typically `/usr/local/mysql/data' for a binary distribution, `/usr/local/var' for a source distribution). Look in the data directory for files with names of the form `host_name.err' and `host_name.log' where host_name is the name of your server host. Then check the last few lines of these files:

shell> tail host_name.err
shell> tail host_name.log

When the mysqld daemon starts up, it changes directory to the data directory. This is where it expects to write log files and the pid (process ID) file, and where it expects to find databases.

The data directory location is hardwired in when the distribution is compiled. However, if mysqld expects to find the data directory somewhere other than where it really is on your system, it will not work properly. If you have problems with incorrect paths, you can find out what options mysqld allows and what the default path settings are by invoking mysqld with the --help option. You can override the defaults by specifying the correct pathnames as command-line arguments to mysqld. (These options can be used with safe_mysqld as well.)

Normally you should need to tell mysqld only the base directory under which MySQL is installed. You can do this with the --basedir option. You can also use --help to check the effect of changing path options (note that --help must be the final option of the mysqld command). For example:

shell> EXECDIR/mysqld --basedir=/usr/local --help

Once you determine the path settings you want, start the server without the --help option.

If you get the following error, it means that some other program (or another mysqld server) is already using the TCP/IP port or socket mysqld is trying to use:

Can't start server: Bind on TCP/IP port: Address already in use
  or
Can't start server : Bind on unix socket...

Use ps to make sure that you don't have another mysqld server running. If you can't find another server running, you can try to execute the command telnet your-host-name tcp-ip-port-number and press RETURN a couple of times. If you don't get a error message like telnet: Unable to connect to remote host: Connection refused, something is using the TCP/IP port mysqld is trying to use. See section 4.15.1 Problems running mysql_install_db, and section 19.3 Running multiple MySQL servers on the same machine.

The safe_mysqld script is written so that it normally is able to start a server that was installed from either a source or a binary version of MySQL, even if these install the server in slightly different locations. safe_mysqld expects one of these conditions to be true:

• The server and databases can be found relative to the directory from which safe_mysqld is invoked. safe_mysqld looks under its working directory for `bin' and `data' directories (for binary distributions) or for `libexec' and `var' directories (for source distributions). This condition should be met if you execute safe_mysqld from your MySQL installation directory (for example, `/usr/local/mysql' for a binary distribution).
• If the server and databases cannot be found relative to its working directory, safe_mysqld attempts to locate them by absolute pathnames. Typical locations are `/usr/local/libexec' and `/usr/local/var'. The actual locations are determined when the distribution was built from which safe_mysqld comes. They should be correct if MySQL was installed in a standard location.

Since safe_mysqld will try to find the server and databases relative to its own working directory, you can install a binary distribution of MySQL anywhere, as long as you start safe_mysqld from the MySQL installation directory:

shell> cd mysql_installation_directory
shell> bin/safe_mysqld &

If safe_mysqld fails, even when invoked from the MySQL installation directory, you can modify it to use the path to mysqld and the pathname options that are correct for your system. Note that if you upgrade MySQL in the future, your modified version of safe_mysqld will be overwritten, so you should make a copy of your edited version that you can reinstall.

If mysqld is currently running, you can find out what path settings it is using by executing this command:

shell> mysqladmin variables

or

shell> mysqladmin -h 'your-host-name' variables

If safe_mysqld starts the server but you can't connect to it, you should make sure you have an entry in `/etc/hosts' that looks like this:

127.0.0.1       localhost

This problem occurs only on systems that don't have a working thread library and for which MySQL must be configured to use MIT-pthreads.

4.15.3 Starting and stopping MySQL automatically

The mysql.server script can be used to start or stop the server, by invoking it with start or stop arguments:

shell> mysql.server start
shell> mysql.server stop

mysql.server can be found in the `share/mysql' directory under the MySQL installation directory, or in the `support-files' directory of the MySQL source tree.

Before mysql.server starts the server, it changes directory to the MySQL installation directory, then invokes safe_mysqld. You might need to edit mysql.server if you have a binary distribution that you've installed in a non-standard location. Modify it to cd into the proper directory before it runs safe_mysqld. If you want the server to run as some specific user, you can change the mysql_daemon_user=root line to use another user. You can also modify mysql.server to pass other options to safe_mysqld.

mysql.server stop brings down server by sending a signal to it. You can take down the server manually by executing mysqladmin shutdown.

You might want to add these start and stop commands to the appropriate places in your `/etc/rc*' files when you start using MySQL for production applications. Note that if you modify mysql.server, then if you upgrade MySQL sometime, your modified version will be overwritten, so you should make a copy of your edited version that you can reinstall.

If your system uses `/etc/rc.local' to start external scripts, you should append the following to it:

/bin/sh -c 'cd /usr/local/mysql ; ./bin/safe_mysqld &'

You can also add options for mysql.server in a global `/etc/my.cnf' file. A typical `/etc/my.cnf' file might look like this:

[mysqld]
datadir=/usr/local/mysql/var
socket=/tmp/mysqld.sock
port=3306

[mysql.server]
user=mysql
basedir=/usr/local/mysql

The mysql.server script uses the following variables: user, datadir, basedir, bindir and pid-file.

See section 4.15.4 Option files.

4.15.4 Option files

MySQL 3.22 can read default startup options for the server and for clients from option files.

MySQL reads default options from the following files on Unix:

Filename	Purpose
/etc/my.cnf	Global options
DATADIR/my.cnf	Server-specific options
~/.my.cnf	User-specific options

DATADIR is the MySQL data directory (typically `/usr/local/mysql/data' for a binary installation, or `/usr/local/var' for a source installation). Note that this is the directory that was specified at configuration time, not the one specified with --datadir when mysqld starts up! (--datadir has no effect on where the server looks for option files, because it looks for them before it processes any command-line arguments.)

MySQL reads default options from the following files on Win32:

Note that you on Win32 should specify all paths with / instead of \. If you use \, you need to specify this twice, as \ is the escape character in MySQL.

MySQL tries to read option files in the order listed above. If multiple option files exist, an option specified in a file read later takes precedence over the same option specified in a file read earlier. Options specified on the command line take precedence over options specified in any option file. Some options can be specified using environment variables. Options specified on the command line or in option files take precedence over environment variable values.

The following programs support option files: mysql, mysqladmin, mysqld, mysqldump, mysqlimport, mysql.server, isamchk and pack_isam.

You can use option files to specify any long option that a program supports! Run the program with --help to get a list of available options.

An option file can contain lines of the following forms:

#comment

Comment lines start with `#' or `;'. Empty lines are ignored.

[group]

group is the name of the program or group for which you want to set options. After a group line, any option or set-variable lines apply to the named group until the end of the option file or another group line is given.

option

This is equivalent to --option on the command line.

option=value

This is equivalent to --option=value on the command line.

set-variable = variable=value

This is equivalent to --set-variable variable=value on the command line. This syntax must be used to set a mysqld variable.

The client group allows you to specify options that apply to all MySQL clients (not mysqld). This is the perfect group to use to specify the password you use to connect to the server. (But make sure the option file is readable and writable only to yourself.)

Note that for options and values, all leading and trailing blanks are automatically deleted. You may use the escape sequences `\b', `\t', `\n', `\r', `\\' and `\s' in your value string (`\s' == blank).

Here is a typical global option file:

[client]
port=3306
socket=/tmp/mysql.sock

[mysqld]
port=3306
socket=/tmp/mysql.sock
set-variable = key_buffer=16M
set-variable = max_allowed_packet=1M

[mysqldump]
quick

Here is typical user option file:

[client]
# The following password will be sent to all standard MySQL clients
password=my_password

[mysql]
no-auto-rehash

If you have a source distribution, you will find a sample configuration file named `my-example.cnf' in the `support-files' directory. If you have a binary distribution, look in the `DIR/share/mysql' directory, where DIR is the pathname to the MySQL installation directory (typically `/usr/local/mysql'). You can copy `my-example.cnf' to your home directory (rename the copy to `.my.cnf') to experiment with.

To tell a MySQL program not to read any option files, specify --no-defaults as the first option on the command line. This MUST be the first option or it will have no effect! If you want to check which options are used, you can give the option --print-defaults as the first option.

If you want to force the use of a specific config file, you can use the option --defaults-file=full-path-to-default-file. If you do this, only the specified file will be read.

Note for developers: Option file handling is implemented simply by processing all matching options (i.e., options in the appropriate group) before any command line arguments. This works nicely for programs that use the last instance of an option that is specified multiple times. If you have an old program that handles multiply-specified options this way but doesn't read option files, you need add only two lines to give it that capability. Check the source code of any of the standard MySQL clients to see how to do this.

4.16 Is there anything special to do when upgrading/downgrading MySQL?

You can always move the MySQL form and data files between different versions on the same architecture as long as you have the same base version of MySQL. The current base version is 3. If you change the character set by recompiling MySQL (which may also change the sort order), you must run isamchk -r -q on all tables. Otherwise your indexes may not be ordered correctly.

If you are paranoid and/or afraid of new versions, you can always rename your old mysqld to something like mysqld-'old-version-number'. If your new mysqld then does something unexpected, you can simply shut it down and restart with your old mysqld!

When you do an upgrade you should also backup your old databases, of course. Sometimes it's good to be a little paranoid!

After an upgrade, if you experience problems with recompiled client programs, like Commands out of sync or unexpected core dumps, you probably have used an old header or library file when compiling your programs. In this case you should check the date for your `mysql.h' file and `libmysqlclient.a' library to verify that they are from the new MySQL distribution. If not, please recompile your programs!

If you get some problems that the new mysqld server doesn't want to start or that you can't connect without a password, check that you don't have some old `my.cnf' file from your old installation! You can check this with: program-name --print-defaults. If this outputs anything other than the program name, you have a active my.cnf file that will may affect things!

It is a good idea to rebuild and reinstall the Msql-Mysql-modules distribution whenever you install a new release of MySQL, particularly if you notice symptoms such as all your DBI scripts dumping core after you upgrade MySQL.

4.16.1 Upgrading from a 3.22 version to 3.23

MySQL 3.23 supports tables of the new MyISAM type and the old NISAM type. You don't have to convert your old tables to use these with 3.23. By default, all new tables will be created with type MyISAM (unless you start mysqld with the --default-table-type=isam option. You can change an ISAM table to a MyISAM table with ALTER TABLE or the Perl script mysql_convert_table_format.

3.22 and 3.21 clients will work without any problems with a 3.23 server.

The following lists what you have to watch out for when upgrading to 3.23:

• INNER and DELAYED are now reserved words.
• FLOAT(4) and FLOAT(8) are now true floating point types.
• When declaring DECIMAL(length,dec) the length argument no longer includes a place for the sign or the decimal point.
• A TIME string must now be of one of the following formats: [[[DAYS] [H]H:]MM:]SS[.fraction] or [[[[[H]H]H]H]MM]SS[.fraction]
• LIKE now compares strings using the same character comparison rules as '='. If you require the old behavior, you can compile MySQL with the CXXFLAGS=-DLIKE_CMP_TOUPPER flag.
• REGEXP is now case insensitive for normal (not binary) strings.
• When you check/repair tables you should use myisamchk for MyISAM tables (.MYI) and isamchk for ISAM (.ISM) tables.
• If you want your mysqldumps to be compatible between MySQL 3.22 and 3.23, you should not use the --opt or --full option to mysqldump.
• Check all your calls to DATE_FORMAT() to make sure there is a `%' before each format character.
• mysql_fetch_fields_direct is now a function (it was a macro) and it returns a pointer to a MYSQL_FIELD instead of a MYSQL_FIELD.
• mysql_num_fields() can no longer be used on a MYSQL* object (it's now a function that takes MYSQL_RES* as an argument. You should now use mysql_field_count() instead.
• In MySQL 3.22, the output of SELECT DISTINCT ... was almost always sorted. In 3.23, you must use GROUP BY or ORDER BY to obtain sorted output.
• SUM() now returns NULL, instead of 0, if there is no matching rows. This is according to ANSI SQL.
• New restricted words: CASE, THEN, WHEN, ELSE and END

4.16.2 Upgrading from a 3.21 version to 3.22

Nothing that affects compatibility has changed between 3.21 and 3.22. The only pitfall is that new tables that are created with DATE type columns will use the new way to store the date. You can't access these new fields from an old version of mysqld.

After installing MySQL 3.22, you should start the new server and then run the mysql_fix_privilege_tables script. This will add the new privileges that you need to use the GRANT command. If you forget this, you will get Access denied when you try to use ALTER TABLE, CREATE INDEX or DROP INDEX. If your MySQL root user requires a password, you should give this as an argument to mysql_fix_privilege_tables.

The C API interface to mysql_real_connect() has changed. If you have an old client program that calls this function, you must place a 0 for the new db argument (or recode the client to send the db element for faster connections). You must also call mysql_init() before calling mysql_real_connect()! This change was done to allow the new mysql_options() function to save options in the MYSQL handler structure.

4.16.3 Upgrading from a 3.20 version to 3.21

If you are running a version older than 3.20.28 and want to switch to 3.21.x, you need to do the following:

You can start the mysqld 3.21 server with safe_mysqld --old-protocol to use it with clients from the 3.20 distribution. In this case, the new client function mysql_errno() will not return any server error, only CR_UNKNOWN_ERROR, (but it works for client errors) and the server uses the old password() checking rather than the new one.

If you are NOT using the --old-protocol option to mysqld, you will need to make the following changes:

• All client code must be recompiled. If you are using ODBC, you must get the new MyODBC 2.x driver.
• The script scripts/add_long_password must be run to convert the Password field in the mysql.user table to CHAR(16).
• All passwords must be reassigned in the mysql.user table (to get 62-bit rather than 31-bit passwords).
• The table format hasn't changed, so you don't have to convert any tables.

MySQL 3.20.28 and above can handle the new user table format without affecting clients. If you have a MySQL version earlier than 3.20.28, passwords will no longer work with it if you convert the user table. So to be safe, you should first upgrade to at least 3.20.28 and then upgrade to 3.21.x.

The new client code works with a 3.20.x mysqld server, so if you experience problems with 3.21.x, you can use the old 3.20.x server without having to recompile the clients again.

If you are not using the --old-protocol option to mysqld, old clients will issue the error message:

ERROR: Protocol mismatch. Server Version = 10 Client Version = 9

The new Perl DBI/DBD interface also supports the old mysqlperl interface. The only change you have to make if you use mysqlperl is to change the arguments to the connect() function. The new arguments are: host, database, user, password (the user and password arguments have changed places). See section 20.5.2 The DBI interface.

The following changes may affect queries in old applications:

• HAVING must now be specified before any ORDER BY clause.
• The parameters to LOCATE() have been swapped.
• There are some new reserved words. The most notable are DATE, TIME and TIMESTAMP.

4.16.4 Upgrading to another architecture

If you are using MySQL 3.23, you can copy the .frm, the .MYI and the .MYD files between different architectures that support the same floating point format. (MySQL takes care of any byte swapping issues).

The MySQL data `*.ISD' and the index files `*.ISM' files) are architecture-dependent and in some case OS-dependent. If you want to move your applications to another machine that has a different architecture or OS than your current machine, you should not try to move a database by simply copying the files to the other machine. Use mysqldump instead.

By default, mysqldump will create a file full of SQL statements. You can then transfer the file to the other machine and feed it as input to the mysql client.

Try mysqldump --help to see what options are available. If you are moving the data to a newer version of MySQL, you should use mysqldump --opt with the newer version to get a fast, compact dump.

The easiest (although not the fastest) way to move a database between two machines is to run the following commands on the machine on which the database is located:

shell> mysqladmin -h 'other hostname' create db_name
shell> mysqldump --opt db_name \
        | mysql -h 'other hostname' db_name

If you want to copy a database from a remote machine over a slow network, you can use:

shell> mysqladmin create db_name
shell> mysqldump -h 'other hostname' --opt --compress db_name \
        | mysql db_name

You can also store the result in a file, then transfer the file to the target machine and load the file into the database there. For example, you can dump a database to a file on the source machine like this:

shell> mysqldump --quick db_name | gzip > db_name.contents.gz

(The file created in this example is compressed.) Transfer the file containing the database contents to the target machine and run these commands there:

shell> mysqladmin create db_name
shell> gunzip < db_name.contents.gz | mysql db_name

You can also use mysqldump and mysqlimport to accomplish the database transfer. For big tables, this is much faster than simply using mysqldump. In the commands shown below, DUMPDIR represents the full pathname of the directory you use to store the output from mysqldump.

First, create the directory for the output files and dump the database:

shell> mkdir DUMPDIR
shell> mysqldump --tab=DUMPDIR db_name

Then transfer the files in the DUMPDIR directory to some corresponding directory on the target machine and load the files into MySQL there:

shell> mysqladmin create db_name           # create database
shell> cat DUMPDIR/*.sql | mysql db_name   # create tables in database
shell> mysqlimport db_name DUMPDIR/*.txt   # load data into tables

Also, don't forget to copy the mysql database, since that's where the grant tables (user, db, host) are stored. You may have to run commands as the MySQL root user on the new machine until you have the mysql database in place.

After you import the mysql database on the new machine, execute mysqladmin flush-privileges so that the server reloads the grant table information.

5 How standards-compatible is MySQL?

5.1 MySQL extensions to ANSI SQL92

MySQL includes some extensions that you probably will not find in other SQL databases. Be warned that if you use them, your code will not be portable to other SQL servers. In some cases, you can write code that includes MySQL extensions, but is still portable, by using comments of the form /*! ... */. In this case, MySQL will parse and execute the code within the comment as it would any other MySQL statement, but other SQL servers will ignore the extensions. For example:

SELECT /*! STRAIGHT_JOIN */ col_name FROM table1,table2 WHERE ...

If you add a version number after the '!', the syntax will only be executed if the MySQL version is equal or newer than the used version number:

CREATE /*!32302 TEMPORARY */ TABLE (a int);

The above means that if you have 3.23.02 or newer, then MySQL will use the TEMPORARY keyword.

MySQL extensions are listed below:

• The field types MEDIUMINT, SET, ENUM and the different BLOB and TEXT types.
• The field attributes AUTO_INCREMENT, BINARY, UNSIGNED and ZEROFILL.
• All string comparisons are case insensitive by default, with sort ordering determined by the current character set (ISO-8859-1 Latin1 by default). If you don't like this, you should declare your columns with the BINARY attribute or use the BINARY cast, which causes comparisons to be done according to the ASCII order used on the MySQL server host.
• MySQL maps each database to a directory under the MySQL data directory, and tables within a database to filenames in the database directory. This has two implications:
  • Database names and table names are case sensitive in MySQL on operating systems that have case sensitive filenames (like most Unix systems). If you have a problem remembering table names, adopt a consistent convention, such as always creating databases and tables using lowercase names.
  • Database, table, index, column or alias names may begin with a digit (but may not consist solely of digits).
  • You can use standard system commands to backup, rename, move, delete and copy tables. For example, to rename a table, rename the `.ISD', `.ISM' and `.frm' files to which the table corresponds.
• In SQL statements, you can access tables from different databases with the db_name.tbl_name syntax. Some SQL servers provide the same functionality but call this User space. MySQL dosen't support tablespaces like in: create table ralph.my_table...IN my_tablespace.
• LIKE is allowed on numeric columns.
• Use of INTO OUTFILE and STRAIGHT_JOIN in a SELECT statement. See section 7.11 SELECT syntax.
• The SQL_SMALL_RESULT option in a SELECT statement.
• EXPLAIN SELECT to get a description on how tables are joined.
• Use of index names, indexes on a prefix of a field, and use of INDEX or KEY in a CREATE TABLE statement. See section 7.6 CREATE TABLE syntax.
• Use of TEMPORARY or IF NOT EXISTS with CREATE TABLE.
• Use of COUNT(DISTINCT list) where 'list' is more than one element.
• Use of CHANGE col_name, DROP col_name or DROP INDEX in an ALTER TABLE statement. See section 7.7 ALTER TABLE syntax.
• Use of IGNORE in an ALTER TABLE statement.
• Use of multiple ADD, ALTER, DROP or CHANGE clauses in an ALTER TABLE statement.
• Use of DROP TABLE with the keywords IF EXISTS.
• You can drop multiple tables with a single DROP TABLE statement.
• The LIMIT clause of the DELETE statement.
• The DELAYED clause of the INSERT and REPLACE statements.
• The LOW_PRIORITY clause of the INSERT, REPLACE, DELETE and UPDATE statements.
• Use of LOAD DATA INFILE. In many cases, this syntax is compatible with Oracle's LOAD DATA INFILE. See section 7.15 LOAD DATA INFILE syntax.
• The OPTIMIZE TABLE statement. See section 7.8 OPTIMIZE TABLE syntax.
• The SHOW statement. See section 7.20 SHOW syntax (Get information about tables, columns,...).
• Strings may be enclosed by either `"' or `'', not just by `''.
• Use of the escape `\' character.
• The SET OPTION statement. See section 7.24 SET OPTION syntax.
• You don't need to name all selected columns in the GROUP BY part. This gives better performance for some very specific, but quite normal queries. See section 7.3.13 Functions for use with GROUP BY clauses.
• To make it easier for users that come from other SQL environments, MySQL supports aliases for many functions. For example, all string functions support both ANSI SQL syntax and ODBC syntax.
• MySQL understands the || and && operators to mean logical OR and AND, as in the C programming language. In MySQL, || and OR are synonyms, as are && and AND. Because of this nice syntax, MySQL doesn't support the ANSI SQL || operator for string concatenation; use CONCAT() instead. Since CONCAT() takes any number of arguments, it's easy to convert use of the || operator to MySQL.
• CREATE DATABASE or DROP DATABASE. See section 7.4 CREATE DATABASE syntax.
• The % operator is a synonym for MOD(). That is, N % M is equivalent to MOD(N,M). % is supported for C programmers and for compatibility with PostgreSQL.
• The =, <>, <= ,<, >=,>, <<, >>, <=>, AND, OR or LIKE operators may be used in column comparisons to the left of the FROM in SELECT statements. For example:

  mysql> SELECT col1=1 AND col2=2 FROM tbl_name;
  

• The LAST_INSERT_ID() function. See section 20.4.29 mysql_insert_id().
• The REGEXP and NOT REGEXP extended regular expression operators.
• CONCAT() or CHAR() with one argument or more than two arguments. (In MySQL, these functions can take any number of arguments.)
• The BIT_COUNT(), CASE, ELT(), FROM_DAYS(), FORMAT(), IF(), PASSWORD(), ENCRYPT(), md5(), ENCODE(), DECODE(), PERIOD_ADD(), PERIOD_DIFF(), TO_DAYS(), or WEEKDAY() functions.
• Use of TRIM() to trim substrings. ANSI SQL only supports removal of single characters.
• The GROUP BY functions STD(), BIT_OR() and BIT_AND().
• Use of REPLACE instead of DELETE + INSERT. See section 7.14 REPLACE syntax.
• The FLUSH flush_option statement.

5.2 MySQL differences compared to ANSI SQL92

We try to make MySQL follow the ANSI SQL standard and the ODBC SQL standard, but in some cases MySQL does some things differently:

• -- is only a comment if followed by a white space. See section 5.3.7 `--' as the start of a comment.
• For VARCHAR columns, trailing spaces are removed when the value is stored. See section E Known errors and design deficiencies in MySQL.
• In some cases, CHAR columns are silently changed to VARCHAR columns. See section 7.6.1 Silent column specification changes.
• Privileges for a table is not automatically revoked when you delete a table. You must explicitly issue a REVOKE to revoke privileges for a table. See section 7.25 GRANT and REVOKE syntax.

5.3 Functionality missing from MySQL

The following functionality is missing in the current version of MySQL. For a prioritized list indicating when new extensions may be added to MySQL, you should consult the online MySQL TODO list. That is the latest version of the TODO list in this manual. See section F List of things we want to add to MySQL in the future (The TODO).

5.3.1 Sub-selects

The following will not yet work in MySQL:

SELECT * FROM table1 WHERE id IN (SELECT id FROM table2);
SELECT * FROM table1 WHERE id NOT IN (SELECT id FROM table2);

However, in many cases you can rewrite the query without a sub select:

SELECT table1.* FROM table1,table2 WHERE table1.id=table2.id;
SELECT table1.* FROM table1 LEFT JOIN table2 ON table1.id=table2.id where table2.id IS NULL

For more complicated sub queries you can create temporary tables to hold the sub query.

MySQL only supports INSERT ... SELECT ... and REPLACE ... SELECT ... Independent sub-selects will be probably be available in 3.24.0. You can now use the function IN() in other contexts, however.

5.3.2 SELECT INTO TABLE

MySQL doesn't yet support the Oracle SQL extension: SELECT ... INTO TABLE .... MySQL supports instead the ANSI SQL syntax INSERT INTO ... SELECT ..., which is basically the same thing.

Alternatively, you can use SELECT INTO OUTFILE... or CREATE TABLE ... SELECT to solve your problem.

5.3.3 Transactions

Transactions are not supported. MySQL shortly will support atomic operations, which are like transactions without rollback. With atomic operations, you can execute a group of INSERT/SELECT/whatever commands and be guaranteed that no other thread will interfere. In this context, you won't usually need rollback. Currently, you can prevent interference from other threads by using the LOCK TABLES and UNLOCK TABLES commands. See section 7.23 LOCK TABLES/UNLOCK TABLES syntax.

5.3.4 Stored procedures and triggers

A stored procedure is a set of SQL commands that can be compiled and stored in the server. Once this has been done, clients don't need to keep reissuing the entire query but can refer to the stored procedure. This provides better performance because the query has to be parsed only once and less information needs to be sent between the server and the client. You can also raise the conceptual level by having libraries of functions in the server.

A trigger is a stored procedure that is invoked when a particular event occurs. For example, you can install a stored procedure that is triggered each time a record is deleted from a transaction table and that automatically deletes the corresponding customer from a customer table when all his transactions are deleted.

The planned update language will be able to handle stored procedures, but without triggers. Triggers usually slow down everything, even queries for which they are not needed.

To see when MySQL might get stored procedures, see section F List of things we want to add to MySQL in the future (The TODO).

5.3.5 Foreign Keys

Note that foreign keys in SQL are not used to join tables, but are used mostly for checking referential integrity. If you want to get results from multiple tables from a SELECT statement, you do this by joining tables!

SELECT * from table1,table2 where table1.id = table2.id;

See section 7.12 JOIN syntax. See section 8.3.5 Using foreign keys.

The FOREIGN KEY syntax in MySQL exists only for compatibility with other SQL vendors' CREATE TABLE commands; it doesn't do anything. The FOREIGN KEY syntax without ON DELETE ... is mostly used for documentation purposes. Some ODBC applications may use this to produce automatic WHERE clauses, but this is usually easy to override. FOREIGN KEY is sometimes used as a constraint check, but this check is unnecessary in practice if rows are inserted into the tables in the right order. MySQL only supports these clauses because some applications require them to exist (regardless of whether or not they work!).

In MySQL, you can work around the problem of ON DELETE ... not being implemented by adding the appropriate DELETE statement to an application when you delete records from a table that has a foreign key. In practice this is as quick (in some cases quicker) and much more portable than using foreign keys.

In the near future we will extend the FOREIGN KEY implementation so that at least the information will be saved in the table specification file and may be retrieved by mysqldump and ODBC.

5.3.5.1 Reasons NOT to use foreign keys

There are so many problems with FOREIGN KEYs that we don't know where to start:

• Foreign keys make life very complicated, because the foreign key definitions must be stored in a database and implementing them would destroy the whole "nice approach" of using files that can be moved, copied and removed.
• The speed impact is terrible for INSERT and UPDATE statements, and in this case almost all FOREIGN KEY checks are useless because you usually insert records in the right tables in the right order, anyway.
• There is also a need to hold locks on many more tables when updating one table, because the side effects can cascade through the entire database. It's MUCH faster to delete records from one table first and subsequently delete them from the other tables.
• You can no longer restore a table by doing a full delete from the table and then restoring all records (from a new source or from a backup).
• If you have foreign keys you can't dump and restore tables unless you do so in a very specific order.
• It's very easy to do "allowed" circular definitions that make the tables impossible to recreate each table with a single create statement, even if the definition works and is usable.

The only nice aspect of FOREIGN KEY is that it gives ODBC and some other client programs the ability to see how a table is connected and to use this to show connection diagrams and to help in building applicatons.

MySQL will soon store FOREIGN KEY definitions so that a client can ask for and receive an answer how the original connection was made. The current `.frm' file format does not have any place for it.

5.3.6 Views

MySQL doesn't support views, but this is on the TODO.

5.3.7 `--' as the start of a comment

Some other SQL databases use `--' to start comments. MySQL has `#' as the start comment character, even if the mysql command line tool removes all lines that start with `--'. You can also use the C comment style /* this is a comment */ with MySQL. See section 7.28 Comment syntax.

MySQL 3.23.3 and above supports the `--' comment style only if the comment is followed by a space. This is because this degenerate comment style has caused many problems with automatically generated SQL queries that have used something like the following code, where we automatically insert the value of the payment for !payment!:

UPDATE tbl_name SET credit=credit-!payment!

What do you think will happen when the value of payment is negative?

Because 1--1 is legal in SQL, we think it is terrible that `--' means start comment.

In MySQL 3.23 you can however use: 1-- This is a comment

The following discussing only concerns you if you are running an MySQL version earlier than 3.23:

If you have a SQL program in a text file that contains `--' comments you should use:

shell> replace " --" " #" < text-file-with-funny-comments.sql \
         | mysql database

instead of the usual:

shell> mysql database < text-file-with-funny-comments.sql

You can also edit the command file "in place" to change the `--' comments to `#' comments:

shell> replace " --" " #" -- text-file-with-funny-comments.sql

Change them back with this command:

shell> replace " #" " --" -- text-file-with-funny-comments.sql

5.4 What standards does MySQL follow?

Entry level SQL92. ODBC level 0-2.

5.5 How to cope without COMMIT/ROLLBACK

MySQL doesn't support COMMIT-ROLLBACK. The problem is that handling COMMIT-ROLLBACK efficiently would require a completely different table layout than MySQL uses today. MySQL would also need extra threads that do automatic cleanups on the tables and the disk usage would be much higher. This would make MySQL about 2-4 times slower than it is today. MySQL is much faster than almost all other SQL databases (typically at least 2-3 times faster). One of the reasons for this is the lack of COMMIT-ROLLBACK.

For the moment, we are much more for implementing the SQL server language (something like stored procedures). With this you would very seldom really need COMMIT-ROLLBACK. This would also give much better performance.

Loops that need transactions normally can be coded with the help of LOCK TABLES, and you don't need cursors when you can update records on the fly.

We have transactions and cursors on the TODO but not quite prioritized. If we implement these, it will be as an option to CREATE TABLE. That means that COMMIT-ROLLBACK will work only on those tables, so that a speed penalty will be imposed on those table only.

We at TcX have a greater need for a real fast database than a 100% general database. Whenever we find a way to implement these features without any speed loss, we will probably do it. For the moment, there are many more important things to do. Check the TODO for how we prioritize things at the moment. (Customers with higher levels of support can alter this, so things may be reprioritized.)

The current problem is actually ROLLBACK. Without ROLLBACK, you can do any kind of COMMIT action with LOCK TABLES. To support ROLLBACK, MySQL would have to be changed to store all old records that were updated and revert everything back to the starting point if ROLLBACK was issued. For simple cases, this isn't that hard to do (the current isamlog could be used for this purpose), but it would be much more difficult to implement ROLLBACK for ALTER/DROP/CREATE TABLE.

To avoid using ROLLBACK, you can use the following strategy:

1. Use LOCK TABLES ... to lock all the tables you want to access.
2. Test conditions.
3. Update if everything is okay.
4. Use UNLOCK TABLES to release your locks.

This is usually a much faster method than using transactions with possible ROLLBACKs, although not always. The only situation this solution doesn't handle is when someone kills the threads in the middle of an update. In this case, all locks will be released but some of the updates may not have been executed.

You can also use functions to update records in a single operation. You can get a very efficient application by using the following techniques:

• Modify fields relative to their current value
• Update only those fields that actually have changed

For example, when we are doing updates to some customer information, we update only the customer data that have changed and test only that none of the changed data, or data that depend on the changed data, have changed compared to the original row. The test for changed data is done with the WHERE clause in the UPDATE statement. If the record wasn't updated, we give the client a message: "Some of the data you have changed have been changed by another user". Then we show the old row versus the new row in a window, so the user can decide which version of the customer record he should use.

This gives us something that is similar to "column locking" but is actually even better, because we only update some of the columns, using values that are relative to their current values. This means that typical UPDATE statements look something like these:

UPDATE tablename SET pay_back=pay_back+'relative change';

UPDATE customer
  SET
    customer_date='current_date',
    address='new address',
    phone='new phone',
    money_he_owes_us=money_he_owes_us+'new_money'
  WHERE
    customer_id=id AND address='old address' AND phone='old phone';

As you can see, this is very efficient and works even if another client has changed the values in the pay_back or money_he_owes_us columns.

In many cases, users have wanted ROLLBACK and/or LOCK TABLES for the purpose of managing unique identifiers for some tables. This can be handled much more efficiently by using an AUTO_INCREMENT column and either the SQL function LAST_INSERT_ID() or the C API function mysql_insert_id(). See section 20.4.29 mysql_insert_id().

At TcX, we have never had any need for row-level locking because we have always been able to code around it. Some cases really need row locking, but they are very few. If you want row-level locking, you can use a flag column in the table and do something like this:

UPDATE tbl_name SET row_flag=1 WHERE id=ID;

MySQL returns 1 for the number of affected rows if the row was found and row_flag wasn't already 1 in the original row.

You can think of it as MySQL changed the above query to:

UPDATE tbl_name SET row_flag=1 WHERE id=ID and row_flag <> 1;

6 The MySQL access privilege system

MySQL has an advanced but non-standard security/privilege system. This section describes how it works.

6.1 What the privilege system does

The primary function of the MySQL privilege system is to authenticate a user connecting from a given host, and to associate that user with select, insert, update and delete privileges on a database.

Additional functionality includes the ability to have an anonymous user and to grant privileges for MySQL-specific functions such as LOAD DATA INFILE and administrative operations.

6.2 MySQL user names and passwords

There are several distinctions between the way user names and passwords are used by MySQL, and the way they are used by Unix or Windows:

• User names, as used by MySQL for authentication purposes, have nothing to do with Unix user names (login names) or Windows user names. Most MySQL clients by default try to log in using the current Unix user name as the MySQL user name, but that is for convenience only. Client programs allow a different name to be specified with the -u or --user options. This means that you can't make a database secure in any way unless all MySQL user names have passwords. Anyone may attempt to connect to the server using any name, and they will succeed if they specify any name that doesn't have a password.
• MySQL user names can be up to 16 characters long; Unix user names typically are limited to 8 characters.
• MySQL passwords have nothing to do with Unix passwords. There is no necessary connection between the password you use to log in to a Unix machine and the password you use to access a database on that machine.
• MySQL encrypts passwords using a different algorithm than the one used during the Unix login process. See the descriptions of the PASSWORD() and ENCRYPT() functions in section 7.3.12 Miscellaneous functions.

6.3 Connecting to the MySQL server

MySQL client programs generally require that you specify connection parameters when you want to access a MySQL server: the host you want to connect to, your user name and your password. For example, the mysql client can be started like this (optional arguments are enclosed between `[' and `]'):

shell> mysql [-h host_name] [-u user_name] [-pyour_pass]

Alternate forms of the -h, -u and -p options are --host=host_name, --user=user_name and --password=your_pass. Note that there is no space between -p or --password= and the password following it.

Note: Specifing a password on the command line is not secure! Any user on your system may then find out your password by typing a command like: ps auxww. See section 4.15.4 Option files.

mysql uses default values for connection parameters that are missing from the command line:

• The default hostname is localhost.
• The default user name is your Unix login name.
• No password is supplied if -p is missing.

Thus, for a Unix user joe, the following commands are equivalent:

shell> mysql -h localhost -u joe
shell> mysql -h localhost
shell> mysql -u joe
shell> mysql

Other MySQL clients behave similarly.

On Unix systems, you can specify different default values to be used when you make a connection, so that you need not enter them on the command line each time you invoke a client program. This can be done in a couple of ways:

• You can specify connection parameters in the [client] section of the `.my.cnf' configuration file in your home directory. The relevant section of the file might look like this:

  [client]
  host=host_name
  user=user_name
  password=your_pass
  

  See section 4.15.4 Option files.
• You can specify connection parameters using environment values. The host can be specified using MYSQL_HOST. The MySQL user name can be specified using USER (this is for Windows only). The password can be specified using MYSQL_PWD (but this is insecure; see next section).

If connection parameters are specified in multiple ways, values specified on the command line take precedence over values specified in configuration files and environment variables, and values in configuration files take precedence over values in environment variables.

6.4 Keeping your password secure

It is inadvisable to specify your password in a way that exposes it to discovery by other users. The methods you can use to specify your password when you run client programs are listed below, along with an assessment of the risks of each method:

• Use a -pyour_pass or --password=your_pass option on the command line. This is convenient but insecure, since your password becomes visible to system status programs (such as ps) that may be invoked by other users to display command lines. (MySQL clients typically overwrite the command line argument with zeroes during their initialization sequence, but there is still a brief interval during which the value is visible.)
• Use a -p or --password option (with no your_pass value specified). In this case, the client program solicits the password from the terminal:

  shell> mysql -u user_name -p
  Enter password: ********
  

  The client echoes `*' characters to the terminal as you enter your password so that onlookers cannot see it. It is more secure to enter your password this way than to specify it on the command line because it is not visible to other users. However, this method of entering a password is suitable only for programs that you run interactively. If you want to invoke a client from a script that runs non-interactively, there is no opportunity to enter the password from the terminal.
• Store your password in a configuration file. For example, you can list your password in the [client] section of the `.my.cnf' file in your home directory:

  [client]
  password=your_pass
  

  If you store your password in `.my.cnf', the file should not be group or world readable or writable. Make sure the file's access mode is 400 or 600. See section 4.15.4 Option files.
• You can store your password in the MYSQL_PWD environment variable, but this method must be considered extremely insecure and should not be used. Some versions of ps include an option to display the environment of running processes; your password will be in plain sight for all to see if you set MYSQL_PWD. Even on systems without such a version of ps, it is unwise to assume there is no other method to observe process environments.

All in all, the safest methods are to have the client program prompt for the password or to specify the password in a properly-protected `.my.cnf' file.

6.5 Privileges provided by MySQL

Privilege information is stored in the user, db, host, tables_priv and columns_priv tables in the mysql database (that is, in the database named mysql). The MySQL server reads the contents of these tables when it starts up and under the circumstances indicated in section 6.9 When privilege changes take effect.

The names used in this manual to refer to the privileges provided by MySQL are shown below, along with the table column name associated with each privilege in the grant tables and the context in which the privilege applies:

The select, insert, update and delete privileges allow you to perform operations on rows in existing tables in a database.

SELECT statements require the select privilege only if they actually retrieve rows from a table. You can execute certain SELECT statements even without permission to access any of the databases on the server. For example, you could use the mysql client as a simple calculator:

mysql> SELECT 1+1;
mysql> SELECT PI()*2;

The index privilege allows you to create or drop (remove) indexes.

The alter privilege allows you to use ALTER TABLE.

The create and drop privileges allow you to create new databases and tables, or to drop (remove) existing databases and tables.

Note that if you grant the drop privilege for the mysql database to a user, that user can drop the database in which the MySQL access privileges are stored!

The grant privilege allows you to give to other users those privileges you yourself possess.

The file privilege gives you permission to read and write files on the server using the LOAD DATA INFILE and SELECT ... INTO OUTFILE statements. Any user to whom this privilege is granted can read or write any file that the MySQL server can read or write.

The remaining privileges are used for administrative operations, which are performed using the mysqladmin program. The table below shows which mysqladmin commands each administrative privilege allows you to execute:

The reload command tells the server to reread the grant tables. The refresh command flushes all tables and opens and closes the log files. flush-privileges is a synonym for reload. The other flush-* commands perform functions similar to refresh but are more limited in scope, and may be preferable in some instances. For example, if you want to flush just the log files, flush-logs is a better choice than refresh.

The shutdown command shuts down the server.

The processlist command displays information about the threads executing within the server. The kill command kills server threads. You can always display or kill your own threads, but you need the process privilege to display or kill threads initiated by other users.

It is a good idea in general to grant privileges only to those users who need them, but you should exercise particular caution in granting certain privileges:

• The grant privilege allows users to give away their privileges to other users. Two users with different privileges and with the grant privilege are able to combine privileges.
• The alter privilege may be used to subvert the privilege system by renaming tables.
• The file privilege can be abused to read any world-readable file on the server into a database table, the contents of which can then be accessed using SELECT.
• The shutdown privilege can be abused to deny service to other users entirely, by terminating the server.
• The process privilege can be used to view the plain text of currently executing queries, including queries that set or change passwords.
• Privileges on the mysql database can be used to change passwords and other access privilege information. (Passwords are stored encrypted, so a malicious user cannot simply read them. However, with sufficient privileges, that same user can replace a password with a different one.)

There are some things that you cannot do with the MySQL privilege system:

• You cannot explicitly specify that a given user should be denied access. That is, you cannot explicitly match a user and then refuse the connection.
• You cannot specify that a user has privileges to create or drop tables in a database but not to create or drop the database itself.

6.6 How the privilege system works

The MySQL privilege system ensures that all users may do exactly the things that they are supposed to be allowed to do. When you connect to a MySQL server, your identity is determined by the host from which you connect and the user name you specify. The system grants privileges according to your identity and what you want to do.

MySQL considers both your hostname and user name in identifying you because there is little reason to assume that a given user name belongs to the same person everywhere on the Internet. For example, the user bill who connects from whitehouse.gov need not be the same person as the user bill who connects from mosoft.com. MySQL handles this by allowing you to distinguish users on different hosts that happen to have the same name: you can grant bill one set of privileges for connections from whitehouse.gov, and a different set of privileges for connections from microsoft.com.

MySQL access control involves two stages:

• Stage 1: The server checks whether or not you are even allowed to connect.
• Stage 2: Assuming you can connect, the server checks each request you issue to see whether or not you have sufficient privileges to perform it. For example, if you try to select rows from a table in a database or drop a table from the database, the server makes sure you have the select privilege for the table or the drop privilege for the database.

The server uses the user, db and host tables in the mysql database at both stages of access control. The fields in these grant tables are shown below:

For the second stage of access control (request verification), the server may, if the request involves tables, additionally consult the tables_priv and columns_priv tables. The fields in these tables are shown below:

Each grant table contains scope fields and privilege fields.

Scope fields determine the scope of each entry in the tables, i.e., the context in which the entry applies. For example, a user table entry with Host and User values of 'thomas.loc.gov' and 'bob' would be used for authenticating connections made to the server by bob from the host thomas.loc.gov. Similarly, a db table entry with Host, User and Db fields of 'thomas.loc.gov', 'bob' and 'reports' would be used when bob connects from the host thomas.loc.gov to access the reports database. The tables_priv and columns_priv tables contain scope fields indicating tables or table/column combinations to which each entry applies.

For access-checking purposes, comparisons of Host values are case insensitive. User, Password, Db and Table_name values are case sensitive. Column_name values are case insensitive in MySQL 3.22.12 or later.

Privilege fields indicate the privileges granted by a table entry, that is, what operations can be performed. The server combines the information in the various grant tables to form a complete description of a user's privileges. The rules used to do this are described in section 6.8 Access control, stage 2: Request verification.

Scope fields are strings, declared as shown below; the default value for each is the empty string:

In the user, db and host tables, all privilege fields are declared as ENUM('N','Y') -- each can have a value of 'N' or 'Y', and the default value is 'N'.

In the tables_priv and columns_priv tables, the privilege fields are declared as SET fields:

Briefly, the server uses the grant tables like this:

• The user table scope fields determine whether to allow or reject incoming connections. For allowed connections, the privilege fields indicate the user's global (superuser) privileges.
• The db and host tables are used together:
  • The db table scope fields determine which users can access which databases from which hosts. The privilege fields determine which operations are allowed.
  • The host table is used as an extension of the db table when you want a given db table entry to apply to several hosts. For example, if you want a user to be able to use a database from several hosts in your network, leave the Host value empty in the user's db table entry, then populate the host table with an entry for each of those hosts. This mechanism is described more detail in section 6.8 Access control, stage 2: Request verification.
• The tables_priv and columns_priv tables are similar to the db table, but are more fine-grained: they apply at the table and column level rather than at the database level.

Note that administrative privileges (reload, shutdown, etc.) are specified only in the user table. This is because administrative operations are operations on the server itself and are not database-specific, so there is no reason to list such privileges in the other grant tables. In fact, only the user table need be consulted to determine whether or not you can perform an administrative operation.

The file privilege is specified only in the user table, too. It is not an administrative privilege as such, but your ability to read or write files on the server host is independent of the database you are accessing.

The mysqld server reads the contents of the grant tables once, when it starts up. Changes to the grant tables take effect as indicated in section 6.9 When privilege changes take effect.

When you modify the contents of the grant tables, it is a good idea to make sure that your changes set up privileges the way you want. For help in diagnosing problems, see section 6.13 Causes of Access denied errors. For advice on security issues, section 6.14 How to make MySQL secure against crackers.

A useful diagnostic tool is the mysqlaccess script, which Yves Carlier has provided for the MySQL distribution. Invoke mysqlaccess with the --help option to find out how it works. Note that mysqlaccess checks access using only the user, db and host tables. It does not check table- or column-level privileges.

6.7 Access control, stage 1: Connection verification

When you attempt to connect to a MySQL server, the server accepts or rejects the connection based on your identity and whether or not you can verify your identity by supplying the correct password. If not, the server denies access to you completely. Otherwise, the server accepts the connection, then enters stage 2 and waits for requests.

Your identity is based on two pieces of information:

• The host from which you connect
• Your MySQL user name

Identity checking is performed using the three user table scope fields (Host, User and Password). The server accepts the connection only if a user table entry matches your hostname and user name, and you supply the correct password.

Values in the user table scope fields may be specified as follows:

• A Host value may be a hostname or an IP number, or 'localhost' to indicate the local host.
• You can use the wildcard characters `%' and `_' in the Host field.
• A Host value of '%' matches any hostname. A blank Host value is equivalent to '%'. Note that these values match any host that can create a connection to your server!
• Wildcard characters are not allowed in the User field, but you can specify a blank value, which matches any name. If the user table entry that matches an incoming connection has a blank user name, the user is considered to be the anonymous user (the user with no name), rather than the name that the client actually specified. This means that a blank user name is used for all further access checking for the duration of the connection (that is, during stage 2).
• The Password field can be blank. This does not mean that any password matches, it means the user must connect without specifying a password.

Non-blank Password values represent encrypted passwords. MySQL does not store passwords in plaintext form for anyone to see. Rather, the password supplied by a user who is attempting to connect is encrypted (using the PASSWORD() function) and compared to the already-encrypted version stored in the user table. If they match, the password is correct.

The examples below show how various combinations of Host and User values in user table entries apply to incoming connections:

Since you can use IP wildcard values in the Host field (e.g., '144.155.166.%' to match every host on a subnet), there is the possibility that someone might try to exploit this capability by naming a host 144.155.166.somewhere.com. To foil such attempts, MySQL disallows matching on hostnames that start with digits and a dot. Thus, if you have a host named something like 1.2.foo.com, its name will never match the Host column of the grant tables. Only an IP number can match an IP wildcard value.

An incoming connection may be matched by more than one entry in the user table. For example, a connection from thomas.loc.gov by fred would be matched by several of the entries just shown above. How does the server choose which entry to use if more than one matches? The server resolves this question by sorting the user table after reading it at startup time, then looking through the entries in sorted order when a user attempts to connect. The first matching entry is the one that is used.

user table sorting works as follows. Suppose the user table looks like this:

+-----------+----------+-
| Host      | User     | ...
+-----------+----------+-
| %         | root     | ...
| %         | jeffrey  | ...
| localhost | root     | ...
| localhost |          | ...
+-----------+----------+-

When the server reads in the table, it orders the entries with the most-specific Host values first ('%' in the Host column means "any host" and is least specific). Entries with the same Host value are ordered with the most-specific User values first (a blank User value means "any user" and is least specific). The resulting sorted user table looks like this:

+-----------+----------+-
| Host      | User     | ...
+-----------+----------+-
| localhost | root     | ...
| localhost |          | ...
| %         | jeffrey  | ...
| %         | root     | ...
+-----------+----------+-

When a connection is attempted, the server looks through the sorted entries and uses the first match found. For a connection from localhost by jeffrey, the entries with 'localhost' in the Host column match first. Of those, the entry with the blank user name matches both the connecting hostname and user name. (The '%'/'jeffrey' entry would have matched, too, but it is not the first match in the table.)

Here is another example. Suppose the user table looks like this:

+----------------+----------+-
| Host           | User     | ...
+----------------+----------+-
| %              | jeffrey  | ...
| thomas.loc.gov |          | ...
+----------------+----------+-

The sorted table looks like this:

+----------------+----------+-
| Host           | User     | ...
+----------------+----------+-
| thomas.loc.gov |          | ...
| %              | jeffrey  | ...
+----------------+----------+-

A connection from thomas.loc.gov by jeffrey is matched by the first entry, whereas a connection from whitehouse.gov by jeffrey is matched by the second.

A common misconception is to think that for a given user name, all entries that explicitly name that user will be used first when the server attempts to find a match for the connection. This is simply not true. The previous example illustrates this, where a connection from thomas.loc.gov by jeffrey is first matched not by the entry containing 'jeffrey' as the User field value, but by the entry with no user name!

If you have problems connecting to the server, print out the user table and sort it by hand to see where the first match is being made.

6.8 Access control, stage 2: Request verification

Once you establish a connection, the server enters stage 2. For each request that comes in on the connection, the server checks whether you have sufficient privileges to perform it, based on the type of operation you wish to perform. This is where the privilege fields in the grant tables come into play. These privileges can come from any of the user, db, host, tables_priv or columns_priv tables. The grant tables are manipulated with GRANT and REVOKE commands. See section 7.25 GRANT and REVOKE syntax. (You may find it helpful to refer to section 6.6 How the privilege system works, which lists the fields present in each of the grant tables.)

The user table grants privileges that are assigned to you on a global basis and that apply no matter what the current database is. For example, if the user table grants you the delete privilege, you can delete rows from any database on the server host! In other words, user table privileges are superuser privileges. It is wise to grant privileges in the user table only to superusers such as server or database administrators. For other users, you should leave the privileges in the user table set to 'N' and grant privileges on a database-specific basis only, using the db and host tables.

The db and host tables grant database-specific privileges. Values in the scope fields may be specified as follows:

• The wildcard characters `%' and `_' can be used in the Host and Db fields of either table.
• A '%' Host value in the db table means "any host." A blank Host value in the db table means "consult the host table for further information."
• A '%' or blank Host value in the host table means "any host."
• A '%' or blank Db value in either table means "any database."
• A blank User value in either table matches the anonymous user.

The db and host tables are read in and sorted when the server starts up (at the same time that it reads the user table). The db table is sorted on the Host, Db and User scope fields, and the host table is sorted on the Host and Db scope fields. As with the user table, sorting puts the most-specific values first and least-specific values last, and when the server looks for matching entries, it uses the first match that it finds.

The tables_priv and columns_priv tables grant table- and column-specific privileges. Values in the scope fields may be specified as follows:

• The wildcard characters `%' and `_' can be used in the Host field of either table.
• A '%' or blank Host value in either table means "any host."
• The Db, Table_name and Column_name fields cannot contain wildcards or be blank in either table.

The tables_priv and columns_priv tables are sorted on the Host, Db and User fields. This is similar to db table sorting, although since only the Host field may contain wildcards, the sorting is simpler.

The request verification process is described below. (If you are familiar with the access-checking source code, you will notice that the description here differs slightly from the algorithm used in the code. The description is equivalent to what the code actually does; it differs only to make the explanation simpler.)

For administrative requests (shutdown, reload, etc.), the server checks only the user table entry, since that is the only table that specifies administrative privileges. Access is granted if the entry allows the requested operation and denied otherwise. For example, if you want to execute mysqladmin shutdown but your user table entry doesn't grant the shutdown privilege to you, access is denied without even checking the db or host tables. (Since they contain no Shutdown_priv column, there is no need to do so.)

For database-related requests (insert, update, etc.), the server first checks the user's global (superuser) privileges by looking in the user table entry. If the entry allows the requested operation, access is granted. If the global privileges in the user table are insufficient, the server determines the user's database-specific privileges by checking the db and host tables:

1. The server looks in the db table for a match on the Host, Db and User fields. Host and User are matched to the connecting user's hostname and MySQL user name. The Db field is matched to the database the user wants to access. If there is no entry for the Host and User, access is denied.
2. If there is a matching db table entry and its Host field is not blank, that entry defines the user's database-specific privileges.
3. If the matching db table entry's Host field is blank, it signifies that the host table enumerates which hosts should be allowed access to the database. In this case, a further lookup is done in the host table to find a match on the Host and Db fields. If no host table entry matches, access is denied. If there is a match, the user's database-specific privileges are computed as the intersection (not the union!) of the privileges in the db and host table entries, i.e., the privileges that are 'Y' in both entries. (This way you can grant general privileges in the db table entry and then selectively restrict them on a host-by-host basis using the host table entries.)

After determining the database-specific privileges granted by the db and host table entries, the server adds them to the global privileges granted by the user table. If the result allows the requested operation, access is granted. Otherwise, the server checks the user's table and column privileges in the tables_priv and columns_priv tables and adds those to the user's privileges. Access is allowed or denied based on the result.

Expressed in boolean terms, the preceding description of how a user's privileges are calculated may be summarized like this:

global privileges
OR (database privileges AND host privileges)
OR table privileges
OR column privileges

It may not be apparent why, if the global user entry privileges are initially found to be insufficient for the requested operation, the server adds those privileges to the database-, table- and column-specific privileges later. The reason is that a request might require more than one type of privilege. For example, if you execute an INSERT ... SELECT statement, you need both insert and select privileges. Your privileges might be such that the user table entry grants one privilege and the db table entry grants the other. In this case, you have the necessary privileges to perform the request, but the server cannot tell that from either table by itself; the privileges granted by both entries must be combined.

The host table can be used to maintain a list of "secure" servers. At TcX, the host table contains a list of all machines on the local network. These are granted all privileges.

You can also use the host table to indicate hosts that are not secure. Suppose you have a machine public.your.domain that is located in a public area that you do not consider secure. You can allow access to all hosts on your network except that machine by using host table entries like this:

+--------------------+----+-
| Host               | Db | ...
+--------------------+----+-
| public.your.domain | %  | ... (all privileges set to 'N')
| %.your.domain      | %  | ... (all privileges set to 'Y')
+--------------------+----+-

Naturally, you should always test your entries in the grant tables (e.g., using mysqlaccess) to make sure your access privileges are actually set up the way you think they are.

6.9 When privilege changes take effect

When mysqld starts, all grant table contents are read into memory and become effective at that point.

Modifications to the grant tables that you perform using GRANT, REVOKE, or SET PASSWORD are noticed by the server immediately.

If you modify the grant tables manually (using INSERT, UPDATE, etc.), you should execute a FLUSH PRIVILEGES statement or run mysqladmin flush-privileges to tell the server to reload the grant tables. Otherwise your changes will have no effect until you restart the server.

When the server notices that the grant tables have been changed, existing client connections are affected as follows:

• Table and column privilege changes take effect with the client's next request.
• Database privilege changes take effect at the next USE db_name command.

Global privilege changes and password changes take effect the next time the client connects.

6.10 Setting up the initial MySQL privileges

After installing MySQL, you set up the initial access privileges by running scripts/mysql_install_db. See section 4.7.1 Quick installation overview. The scripts/mysql_install_db script starts up the mysqld server, then initializes the grant tables to contain the following set of privileges:

• The MySQL root user is created as a superuser who can do anything. Connections must be made from the local host. Note: The initial root password is empty, so anyone can connect as root without a password and be granted all privileges.
• An anonymous user is created that can do anything with databases that have a name of 'test' or starting with 'test_'. Connections must be made from the local host. This means any local user can connect and be treated as the anonymous user.
• Other privileges are denied. For example, normal users can't use mysqladmin shutdown or mysqladmin processlist.

Note: The default privileges are different for Win32. See section 4.12.4 Running MySQL on Win32.

Since your installation is initially wide open, one of the first things you should do is specify a password for the MySQL root user. You can do this as follows (note that you specify the password using the PASSWORD() function):

shell> mysql -u root mysql
mysql> UPDATE user SET Password=PASSWORD('new_password')
           WHERE user='root';
mysql> FLUSH PRIVILEGES;

You can also use the SET PASSWORD statement:

shell> mysql -u root mysql
mysql> SET PASSWORD FOR root=PASSWORD('new_password');

Another way to set the password is by using the mysqladmin command:

shell> mysqladmin -u root password new_password

Note that if you update the password in the user table directly using the first method, you must tell the server to reread the grant tables (with FLUSH PRIVILEGES), since the change will go unnoticed otherwise.

Once the root password has been set, thereafter you must supply that password when you connect to the server as root.

You may wish to leave the root password blank so that you don't need to specify it while you perform additional setup or testing, but be sure to set it before using your installation for any real production work.

See the scripts/mysql_install_db script to see how it sets up the default privileges. You can use this as a basis to see how to add other users.

If you want the initial privileges to be different than those just described above, you can modify mysql_install_db before you run it.

To recreate the grant tables completely, remove all the `*.frm', `*.ISM' and `*.ISD' files in the directory containing the mysql database. (This is the directory named `mysql' under the database directory, which is listed when you run mysqld --help.) Then run the mysql_install_db script, possibly after editing it first to have the privileges you want.

NOTE: For MySQL versions older than 3.22.10, you should NOT delete the `*.frm' files. If you accidentally do this, you should copy them back from your MySQL distribution before running mysql_install_db.

6.11 Adding new user privileges to MySQL

You can add users two different ways: by using GRANT statements or by manipulating the MySQL grant tables directly. The preferred method is to use GRANT statements, because they are more concise and less error-prone.

The examples below show how to use the mysql client to set up new users. These examples assume that privileges are set up according to the defaults described in the previous section. This means that to make changes, you must be on the same machine where mysqld is running, you must connect as the MySQL root user, and the root user must have the insert privilege for the mysql database and the reload administrative privilege. Also, if you have changed the root user password, you must specify it for the mysql commands below.

You can add new users by issuing GRANT statements:

shell> mysql --user=root mysql
mysql> GRANT ALL PRIVILEGES ON *.* TO monty@localhost
           IDENTIFIED BY 'something' WITH GRANT OPTION;
mysql> GRANT ALL PRIVILEGES ON *.* TO monty@"%"
           IDENTIFIED BY 'something' WITH GRANT OPTION;
mysql> GRANT RELOAD,PROCESS ON *.* TO admin@localhost;
mysql> GRANT USAGE ON *.* TO dummy@localhost;

These GRANT statements set up three new users:

monty

A full superuser who can connect to the server from anywhere, but who must use a password ('something' to do so. Note that we must issue GRANT statements for both monty@localhost and monty@"%". If we don't add the entry with localhost, the anonymous user entry for localhost that is created by mysql_install_db will take precedence when we connect from the local host, because it has a more specific Host field value and thuse comes earlier in the user table sort order.

admin

A user who can connect from localhost without a password and who is granted the reload and process administrative privileges. This allows the user to execute the mysqladmin reload, mysqladmin refresh and mysqladmin flush-* commands, as well as mysqladmin processlist . No database-related privileges are granted. They can be granted later by issuing additional GRANT statements.

dummy

A user who can connect without a password, but only from the local host. The global privileges are all set to 'N' -- the USAGE privilege type allows you to set up a user with no privileges. It is assumed that you will grant database-specific privileges later.

You can also add the same user access information directly by issuing INSERT statements and then telling the server to reload the grant tables:

shell> mysql --user=root mysql
mysql> INSERT INTO user VALUES('localhost','monty',PASSWORD('something'),
                'Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y')
mysql> INSERT INTO user VALUES('%','monty',PASSWORD('something'),
                'Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y','Y')
mysql> INSERT INTO user SET Host='localhost',User='admin',
                 Reload_priv='Y', Process_priv='Y';
mysql> INSERT INTO user (Host,User,Password)
                        VALUES('localhost','dummy',");
mysql> FLUSH PRIVILEGES;

Depending on your MySQL version, you may have to use a different number of 'Y' values above (versions prior to 3.22.11 had fewer privilege columns). For the admin user, the more readable extended INSERT syntax that is available starting with 3.22.11 is used.

Note that to set up a superuser, you need only create a user table entry with the privilege fields set to 'Y'. No db or host table entries are necessary.

The privilege columns in the user table were not set explicitly in the last INSERT statement (for the dummy user), so those columns are assigned the default value of 'N'. This is the same thing that GRANT USAGE does.

The following example adds a user custom who can connect from hosts localhost, server.domain and whitehouse.gov. He wants to access the bankaccount database only from localhost, the expenses database only from whitehouse.gov and the customer database from all three hosts. He wants to use the password stupid from all three hosts.

To set up this user's privileges using GRANT statements, run these commands:

shell> mysql --user=root mysql
mysql> GRANT SELECT,INSERT,UPDATE,DELETE,CREATE,DROP
           ON bankaccount.*
           TO custom@localhost
           IDENTIFIED BY 'stupid';
mysql> GRANT SELECT,INSERT,UPDATE,DELETE,CREATE,DROP
           ON expenses.*
           TO custom@whitehouse.gov
           IDENTIFIED BY 'stupid';
mysql> GRANT SELECT,INSERT,UPDATE,DELETE,CREATE,DROP
           ON customer.*
           TO custom@'%'
           IDENTIFIED BY 'stupid';

To set up the user's privileges by modifying the grant tables directly, run these commands (note the FLUSH PRIVILEGES at the end):

shell> mysql --user=root mysql
mysql> INSERT INTO user (Host,User,Password)
       VALUES('localhost','custom',PASSWORD('stupid'));
mysql> INSERT INTO user (Host,User,Password)
       VALUES('server.domain','custom',PASSWORD('stupid'));
mysql> INSERT INTO user (Host,User,Password)
       VALUES('whitehouse.gov','custom',PASSWORD('stupid'));
mysql> INSERT INTO db
       (Host,Db,User,Select_priv,Insert_priv,Update_priv,Delete_priv,
        Create_priv,Drop_priv)
       VALUES
       ('localhost','bankaccount','custom','Y','Y','Y','Y','Y','Y');
mysql> INSERT INTO db
       (Host,Db,User,Select_priv,Insert_priv,Update_priv,Delete_priv,
        Create_priv,Drop_priv)
       VALUES
       ('whitehouse.gov','expenses','custom','Y','Y','Y','Y','Y','Y');
mysql> INSERT INTO db
       (Host,Db,User,Select_priv,Insert_priv,Update_priv,Delete_priv,
        Create_priv,Drop_priv)
       VALUES('%','customer','custom','Y','Y','Y','Y','Y','Y');
mysql> FLUSH PRIVILEGES;

The first three INSERT statements add user table entries that allow user custom to connect from the various hosts with the given password, but grant no permissions to him (all privileges are set to the default value of 'N'). The next three INSERT statements add db table entries that grant privileges to custom for the bankaccount, expenses and customer databases, but only when accessed from the proper hosts. As usual, when the grant tables are modified directly, the server must be told to reload them (with FLUSH PRIVILEGES) so that the privilege changes take effect.

If you want to give a specific user access from any machine in a given domain, you can issue a GRANT statement like the following:

mysql> GRANT ...
           ON *.*
           TO myusername@"%.mydomainname.com"
           IDENTIFIED BY 'mypassword';

To do the same thing by modifying the grant tables directly, do this:

mysql> INSERT INTO user VALUES ('%.mydomainname.com', 'myusername',
           PASSWORD('mypassword'),...);
mysql> FLUSH PRIVILEGES;

You can also use xmysqladmin, mysql_webadmin and even xmysql to insert, change and update values in the grant tables. You can find these utilities at the MySQL Contrib directory.

6.12 How to set up passwords

The examples in the preceding sections illustrate an important principle: when you store a non-empty password using INSERT or UPDATE statements, you must use the PASSWORD() function to encrypt it. This is because the user table stores passwords in encrypted form, not as plaintext. If you forget that fact, you are likely to attempt to set passwords like this:

shell> mysql -u root mysql
mysql> INSERT INTO user (Host,User,Password)
       VALUES('%','jeffrey','biscuit');
mysql> FLUSH PRIVILEGES;

The result is that the plaintext value 'biscuit' is stored as the password in the user table. When the user jeffrey attempts to connect to the server using this password, the mysql client encrypts it with PASSWORD() and sends the result to the server. The server compares the value in the user table (which is the plaintext value 'biscuit') to the encrypted password (which is not 'biscuit'). The comparison fails and the server rejects the connection:

shell> mysql -u jeffrey -pbiscuit test
Access denied

Since passwords must be encrypted when they are inserted in the user table, the INSERT statement should have been specified like this instead:

mysql> INSERT INTO user (Host,User,Password)
       VALUES('%','jeffrey',PASSWORD('biscuit'));

You must also use the PASSWORD() function when you use SET PASSWORD statements:

mysql> SET PASSWORD FOR jeffrey@"%" = PASSWORD('biscuit');

If you set passwords using the GRANT ... IDENTIFIED BY statement or the mysqladmin password command, the PASSWORD() function is unnecessary. They both take care of encrypting the password for you, so you would specify a password of 'biscuit' like this:

mysql> GRANT USAGE ON *.* TO jeffrey@"%" IDENTIFIED BY 'biscuit';

or

shell> mysqladmin -u jeffrey password biscuit

Note: PASSWORD() does not perform password encryption in the same way that Unix passwords are encrypted. You should not assume that if your Unix password and your MySQL password are the same, PASSWORD() will result in the same encrypted value as is stored in the Unix password file. See section 6.2 MySQL user names and passwords.

6.13 Causes of Access denied errors

If you encounter Access denied errors when you try to connect to the MySQL server, the list below indicates some courses of action you can take to correct the problem:

• Did you run the mysql_install_db script after installing MySQL, to set up the initial grant table contents? If not, do so. See section 6.10 Setting up the initial MySQL privileges. Test the initial privileges by executing this command:

  shell> mysql -u root test
  

  The server should let you connect without error. You should also make sure you have a file `user.ISD' in the MySQL database directory. Ordinarily, this is `PATH/var/mysql/user.ISD', where PATH is the pathname to the MySQL installation root.
• After a fresh installation, you should connect to the server and set up your users and their access permissions:

  shell> mysql -u root mysql
  

  The server should let you connect because the MySQL root user has no password initially. Since that is also a security risk, setting the root password is something you should do while you're setting up your other MySQL users. If you try to connect as root and get this error:

  Access denied for user: '@unknown' to database mysql
  

  this means that you don't have an entry in the user table with a User column value of 'root' and that mysqld cannot resolve the hostname for your client. In this case, you must restart the server with the --skip-grant-tables option and edit your `/etc/hosts' or `\windows\hosts' file to add a entry for your host.
• If you updated an existing MySQL installation from a pre-3.22.11 version to 3.22.11 or later, did you run the mysql_fix_privilege_tables script? If not, do so. The structure of the grant tables changed with MySQL 3.22.11 when the GRANT statement became functional.
• If you make changes to the grant tables directly (using INSERT or UPDATE statement) and your changes seem to be ignored, remember that you must issue a FLUSH PRIVILEGES statement or execute a mysqladmin flush-privileges command to cause the server to reread the tables. Otherwise your changes have no effect until the next time the server is restarted. Remember that after you set the root password, you won't need to specify it until after you flush the privileges, because the server still won't know you've changed the password yet!
• If your privileges seem to have changed in the middle of a session, it may be that a superuser has changed them. Reloading the grant tables affects new client connections, but it also affects existing connections as indicated in section 6.9 When privilege changes take effect.
• For testing, start the mysqld daemon with the --skip-grant-tables option. Then you can change the MySQL grant tables and use the mysqlaccess script to check whether or not your modifications have the desired effect. When you are satisfied with your changes, execute mysqladmin flush-privileges to tell the mysqld server to start using the new grant tables. Note: Reloading the grant tables overrides the --skip-grant-tables option. This allows you to tell the server to begin using the grant tables again without bringing it down and restarting it.
• If you have access problems with a Perl, Python or ODBC program, try to connect to the server with mysql -u user_name db_name or mysql -u user_name -pyour_pass db_name. If you are able to connect using the mysql client, there is a problem with your program and not with the access privileges. (Notice that there is no space between -p and the password; you can also use the --password=your_pass syntax to specify the password.)
• If you can't get your password to work, remember that you must use the PASSWORD() function if you set the password with the INSERT, UPDATE or SET PASSWORD statements. The PASSWORD() function is unnecessary if you specify the password using the GRANT ... INDENTIFIED BY statement or the mysqladmin password command. See section 6.12 How to set up passwords.
• localhost is a synonym for your local hostname, and is also the default host to which clients try to connect if you specify no host explicitly. However, connections to localhost do not work if you are running on a system that uses MIT-pthreads (localhost connections are made using Unix sockets, which are not supported by MIT-pthreads). To avoid this problem on such systems, you should use the --host option to name the server host explicitly. This will make a TCP/IP connection to the mysqld server. In this case, you must have your real hostname in user table entries on the server host. (This is true even if you are running a client program on the same host as the server.)
• If you get an Access denied error when trying to connect to the database with mysql -u user_name db_name, you may have a problem with the user table. Check this by executing mysql -u root mysql and issuing this SQL statement:

  mysql> SELECT * FROM user;
  

  The result should include an entry with the Host and User columns matching your computer's hostname and your MySQL user name.
• The Access denied error message will tell you who you are trying to log in as, the host from which you are trying to connect, and whether or not you were using a password. Normally, you should have one entry in the user table that exactly matches the hostname and user name that were given in the error message.
• If you get the following error when you try to connect from a different host than the one on which the MySQL server is running, then there is no row in the user table that matches that host:

  Host ... is not allowed to connect to this MySQL server
  

  You can fix this by using the command line tool mysql (on the server host!) to add a row to the user table for the user/hostname combination from which you are trying to connect. If you are not running MySQL 3.22 and you don't know the IP number or hostname of the machine from which you are connecting, you should put an entry with '%' as the Host column value in the user table and restart mysqld with the --log option on the server machine. After trying to connect from the client machine, the information in the MySQL log will indicate how you really did connect. (Then replace the '%' in the user table entry with the actual hostname that shows up in the log. Otherwise, you'll have a system that is insecure.)
• If mysql -u root test works but mysql -h your_hostname -u root test results in Access denied, then you may not have the correct name for your host in the user table. A common problem here is that the Host value in the user table entry specifies an unqualified hostname, but your system's name resolution routines return a fully-qualified domain name (or vice-versa). For example, if you have an entry with host 'tcx' in the user table, but your DNS tells MySQL that your hostname is 'tcx.subnet.se', the entry will not work. Try adding an entry to the user table that contains the IP number of your host as the Host column value. (Alternatively, you could add an entry to the user table with a Host value that contains a wildcard--for example, 'tcx.%'. However, use of hostnames ending with `%' is insecure and is not recommended!)
• If mysql -u user_name test works but mysql -u user_name other_db_name doesn't work, you don't have an entry for other_db_name listed in the db table.
• If mysql -u user_name db_name works when executed on the server machine, but mysql -u host_name -u user_name db_name doesn't work when executed on another client machine, you don't have the client machine listed in the user table or the db table.
• If you can't figure out why you get Access denied, remove from the user table all entries that have Host values containing wildcards (entries that contain `%' or `_'). A very common error is to insert a new entry with Host='%' and User='some user', thinking that this will allow you to specify localhost to connect from the same machine. The reason that this doesn't work is that the default privileges include an entry with Host='localhost' and User=". Since that entry has a Host value 'localhost' that is more specific than '%', it is used in preference to the new entry when connecting from localhost! The correct procedure is to insert a second entry with Host='localhost' and User='some_user', or to remove the entry with with Host='localhost' and User=".
• If you get the following error, you may have a problem with the db or host table:

  Access to database denied
  

  If the entry selected from the db table has an empty value in the Host column, make sure there are one or more corresponding entries in the host table specifying which hosts the db table entry applies to. If you get the error when using the SQL commands SELECT ... INTO OUTFILE or LOAD DATA INFILE, your entry in the user table probably doesn't have the file privilege enabled.
• Remember that client programs will use connection parameters specified in configuration files or environment variables. If a client seems to be sending the wrong default connection parameters when you don't specify them on the command line, check your environment and the `.my.cnf' file in your home directory. You might also check the system-wide MySQL configuration files, though it is far less likely that client connection parameters will be specified there. See section 4.15.4 Option files. If you get Access denied when you run a client without any options, make sure you haven't specified an old password in any of your option files! See section 4.15.4 Option files.
• If everything else fails, start the mysqld daemon with a debugging option (for example, --debug=d,general,query). This will print host and user information about attempted connections, as well as information about each command issued. See section G.1 Debugging a MySQL server.
• If you have any other problems with the MySQL grant tables and feel you must post the problem to the mailing list, always provide a dump of the MySQL grant tables. You can dump the tables with the mysqldump mysql command. As always, post your problem using the mysqlbug script. In some cases you may restart mysqld with --skip-grant-tables to be able to run mysqldump.

6.14 How to make MySQL secure against crackers

When you connect to a MySQL server, you should normally use a password. The password is not transmitted in clear text over the connection.

All other information is transferred as text that can be read by anyone that is able to watch the connection. If you are concerned about this, you can use the compressed protocol (in MySQL 3.22 and above) to make things much harder. To make things even more secure you should install ssh (see http://www.cs.hut.fi/ssh). With this, you can get an encrypted TCP/IP connection between a MySQL server and a MySQL client.

To make a MySQL system secure, you should strongly consider the following suggestions:

• Use passwords for all MySQL users. Remember that anyone can log in as any other person as simply as mysql -u other_user db_name if other_user has no password. It is common behavior with client/server applications that the client may specify any user name. You can change the password of all users by editing the mysql_install_db script before you run it, or only the password for the MySQL root user like this:

  shell> mysql -u root mysql
  mysql> UPDATE user SET Password=PASSWORD('new_password')
             WHERE user='root';
  mysql> FLUSH PRIVILEGES;
  

• Don't run the MySQL daemon as the Unix root user. mysqld can be run as any user. You can also create a new Unix user mysql to make everything even more secure. If you run mysqld as another Unix user, you don't need to change the root user name in the user table, because MySQL user names have nothing to do with Unix user names. You can edit the mysql.server script to start mysqld as another Unix user. Normally this is done with the su command. For more details, see section 18.8 How to run MySQL as a normal user.
• If you put a password for the Unix root user in the mysql.server script, make sure this script is readable only by root.
• Check that the Unix user that mysqld runs as is the only user with read/write privileges in the database directories.
• Don't give the process privilege to all users. The output of mysqladmin processlist shows the text of the currently executing queries, so any user who is allowed to execute that command might be able to see if another user issues an UPDATE user SET password=PASSWORD('not_secure') query. mysqld saves an extra connection for users who have the process privilege, so that a MySQL root user can log in and check things even if all normal connections are in use.
• Don't give the file privilege to all users. Any user that has this privilege can write a file anywhere in the file system with the privileges of the mysqld daemon! To make this a bit safer, all files generated with SELECT ... INTO OUTFILE are readable to everyone, and you can't overwrite existing files. The file privilege may also be used to read any file accessible to the Unix user that the server runs as. This could be abused, for example, by using LOAD DATA to load `/etc/passwd' into a table, which can then be read with SELECT.
• If you don't trust your DNS, you should use IP numbers instead of hostnames in the grant tables. In principle, the --secure option to mysqld should make hostnames safe. In any case, you should be very careful about using hostname values that contain wildcards!

The following mysqld options affect security:

--secure

IP numbers returned by the gethostbyname() system call are checked to make sure they resolve back to the original hostname. This makes it harder for someone on the outside to get access by simulating another host. This option also adds some sanity checks of hostnames. The option is turned off by default in MySQL 3.21 since it sometimes takes a long time to perform backward resolutions. MySQL 3.22 caches hostnames and has this option enabled by default.

--skip-grant-tables

This option causes the server not to use the privilege system at all. This gives everyone full access to all databases! (You can tell a running server to start using the grant tables again by executing mysqladmin reload.)

--skip-name-resolve

Hostnames are not resolved. All Host column values in the grant tables must be IP numbers or localhost.

--skip-networking

Don't allow TCP/IP connections over the network. All connections to mysqld must be made via Unix sockets. This option is unsuitable for systems that use MIT-pthreads, because the MIT-pthreads package doesn't support Unix sockets.

7 MySQL language reference

7.1 Literals: how to write strings and numbers

7.1.1 Strings

A string is a sequence of characters, surrounded by either single quote (`'') or double quote (`"') characters. Examples:

'a string'
"another string"

Within a string, certain sequences have special meaning. Each of these sequences begins with a backslash (`\'), known as the escape character. MySQL recognizes the following escape sequences:

\0

An ASCII 0 (NUL) character.

\n

A newline character.

\t

A tab character.

\r

A carriage return character.

\b

A backspace character.

\'

A single quote (`'') character.

\"

A double quote (`"') character.

\\

A backslash (`\') character.

\%

A `%' character. This is used to search for literal instances of `%' in contexts where `%' would otherwise be interpreted as a wildcard character.

\_

A `_' character. This is used to search for literal instances of `_' in contexts where `_' would otherwise be interpreted as a wildcard character.

Note that if you use `\%' or `\%_' in some string contexts, these will return the strings `\%' and `\_' and not `%' and `_'.

There are several ways to include quotes within a string:

• A `'' inside a string quoted with `'' may be written as `"'.
• A `"' inside a string quoted with `"' may be written as `""'.
• You can precede the quote character with an escape character (`\').
• A `'' inside a string quoted with `"' needs no special treatment and need not be doubled or escaped. In the same way, `"' inside a string quoted with `'' needs no special treatment.

The SELECT statements shown below demonstrate how quoting and escaping work:

mysql> SELECT 'hello', '"hello"', '""hello""', 'hel"lo', '\'hello';
+-------+---------+-----------+--------+--------+
| hello | "hello" | ""hello"" | hel'lo | 'hello |
+-------+---------+-----------+--------+--------+

mysql> SELECT "hello", "'hello'", ""hello"", "hel""lo", "\"hello";
+-------+---------+-----------+--------+--------+
| hello | 'hello' | "hello" | hel"lo | "hello |
+-------+---------+-----------+--------+--------+

mysql> SELECT "This\nIs\nFour\nlines";
+--------------------+
| This
Is
Four
lines |
+--------------------+

If you want to insert binary data into a BLOB column, the following characters must be represented by escape sequences:

NUL

ASCII 0. You should represent this by `\0' (a backslash and an ASCII `0' character).

\

ASCII 92, backslash. Represent this by `\\'.

'

ASCII 39, single quote. Represent this by `\''.

"

ASCII 34, double quote. Represent this by `\"'.

If you write C code, you can use the C API function mysql_escape_string() to escape characters for the INSERT statement. See section 20.3 C API function overview. In Perl, you can use the quote method of the DBI package to convert special characters to the proper escape sequences. See section 20.5.2 The DBI interface.

You should use an escape function on any string that might contain any of the special characters listed above!

7.1.2 Numbers

Integers are represented as a sequence of digits. Floats use `.' as a decimal separator. Either type of number may be preceded by `-' to indicate a negative value.

Examples of valid integers:

1221
0
-32

Examples of valid floating-point numbers:

294.42
-32032.6809e+10
148.00

An integer may be used in a floating-point context; it is interpreted as the equivalent floating-point number.

7.1.3 Hexadecimal values

MySQL supports hexadecimal values. In number context these acts like an integer (64 bit precision). In string context these acts like a binary string where each pair of hex digits is converted to a character.

mysql> SELECT 0xa+0
       -> 10
mysql> select 0x5061756c;
       -> Paul

Hexadecimal strings is often used by ODBC to give values for BLOB columns.

7.1.4 NULL values

The NULL value means "no data" and is different from values such as 0 for numeric types or the empty string for string types. See section 18.15 Problems with NULL values.

NULL may be represented by \N when using the text file import or export formats (LOAD DATA INFILE, SELECT ... INTO OUTFILE). See section 7.15 LOAD DATA INFILE syntax.

7.1.5 Database, table, index, column and alias names

Database, table, index, column and alias names all follow the same rules in MySQL:

• A name may consist of alphanumeric characters from the current character set and also `_' and `$'. The default character set is ISO-8859-1 Latin1; this may be changed by recompiling MySQL. See section 9.1.1 The character set used for data and sorting.
• A database, table, index or column name can be up to 64 characters long. An alias name can be up to 256 characters long.
• A name may start with any character that is legal in a name. In particular, a name may start with a number (this differs from many other database systems!). However, a name cannot consist only of numbers.
• It is recommended that you do not use names like 1e, because an expression like 1e+1 is ambiguous. It may be interpreted as the expression 1e + 1 or as the number 1e+1.
• You cannot use the `.' character in names because it is used to extend the format by which you can refer to columns (see immediately below).

In MySQL you can refer to a column using any of the following forms:

You need not specify a tbl_name or db_name.tbl_name prefix for a column reference in a statement unless the reference would be ambiguous. For example, suppose tables t1 and t2 each contain a column c, and you retrieve c in a SELECT statement that uses both t1 and t2. In this case, c is ambiguous because it is not unique among the tables used in the statement, so you must indicate which table you mean by writing t1.c or t2.c. Similarly, if you are retrieving from a table t in database db1 and from a table t in database db2, you must refer to columns in those tables as db1.t.col_name and db2.t.col_name.

The syntax .tbl_name means the table tbl_name in the current database. This syntax is accepted for ODBC compatibility, because some ODBC programs prefix table names with a `.' character.

7.1.5.1 Case sensitivity in names

In MySQL, databases and tables correspond to directories and files within those directories. Consequently, the case sensitivity of the underlying operating system determines the case sensitivity of database and table names. This means database and table names are case sensitive in Unix and case insensitive in Win32.

Note: Although database and table names are case insensitive for Win32, you should not refer to a given database or table using different cases within the same query. The following query would not work because it refers to a table both as my_table and as MY_TABLE:

mysql> SELECT * FROM my_table WHERE MY_TABLE.col=1;

Column names are case insensitive in all cases.

Aliases on tables are case sensitive. The following query would not work because it refers to the alias both as a and as A:

mysql> SELECT col_name FROM tbl_name AS a
           WHERE a.col_name = 1 OR A.col_name = 2;

Aliases on columns are case insensitive.

7.2 Column types

MySQL supports a number of column types, which may be grouped into three categories: numeric types, date and time types, and string (character) types. This section first gives an overview of the types available and summarizes the storage requirements for each column type, then provides a more detailed description of the properties of the types in each category. The overview is intentionally brief. The more detailed descriptions should be consulted for additional information about particular column types, such as the allowable formats in which you can specify values.

The column types supported by MySQL are listed below. The following code letters are used in the descriptions:

M

Indicates the maximum display size. The maximum legal display size is 255.

D

Applies to floating-point types and indicates the number of digits following the decimal point. The maximum possible value is 30, but should be no greater than M-2.

Square brackets (`[' and `]') indicate parts of type specifiers that are optional.

Note that if you specify ZEROFILL for a column, MySQL will automatically add the UNSIGNED attribute to the column.

TINYINT[(M)] [UNSIGNED] [ZEROFILL]

A very small integer. The signed range is -128 to 127. The unsigned range is 0 to 255.

SMALLINT[(M)] [UNSIGNED] [ZEROFILL]

A small integer. The signed range is -32768 to 32767. The unsigned range is 0 to 65535.

MEDIUMINT[(M)] [UNSIGNED] [ZEROFILL]

A medium-size integer. The signed range is -8388608 to 8388607. The unsigned range is 0 to 16777215.

INT[(M)] [UNSIGNED] [ZEROFILL]

A normal-size integer. The signed range is -2147483648 to 2147483647. The unsigned range is 0 to 4294967295.

INTEGER[(M)] [UNSIGNED] [ZEROFILL]

This is a synonym for INT.

BIGINT[(M)] [UNSIGNED] [ZEROFILL]

A large integer. The signed range is -9223372036854775808 to 9223372036854775807. The unsigned range is 0 to 18446744073709551615. Note that all arithmetic is done using signed BIGINT or DOUBLE values, so you shouldn't use unsigned big integers larger than 9223372036854775807 (63 bits) except with bit functions! Note that -, + and * will use BIGINT arithmetic when both arguments are INTEGER values! This means that if you multiply two big integers (or results from functions that return integers) you may get unexpected results if the result is larger than 9223372036854775807.

FLOAT(precision) [ZEROFILL]

A floating-point number. Cannot be unsigned. precision can be 4 or 8. FLOAT(4) is a single-precision number and FLOAT(8) is a double-precision number. These types are like the FLOAT and DOUBLE types described immediately below. FLOAT(4) and FLOAT(8) have the same ranges as the corresponding FLOAT and DOUBLE types, but their display size and number of decimals is undefined. In MySQL 3.23, this is a true floating point value. In earlier MySQL versions, FLOAT(precision) always has 2 decimals. This syntax is provided for ODBC compatibility.

FLOAT[(M,D)] [ZEROFILL]

A small (single-precision) floating-point number. Cannot be unsigned. Allowable values are -3.402823466E+38 to -1.175494351E-38, 0 and 1.175494351E-38 to 3.402823466E+38.

DOUBLE[(M,D)] [ZEROFILL]

A normal-size (double-precision) floating-point number. Cannot be unsigned. Allowable values are -1.7976931348623157E+308 to -2.2250738585072014E-308, 0 and 2.2250738585072014E-308 to 1.7976931348623157E+308.

DOUBLE PRECISION[(M,D)] [ZEROFILL]

REAL[(M,D)] [ZEROFILL]

These are synonyms for DOUBLE.

DECIMAL(M,D) [ZEROFILL]

An unpacked floating-point number. Cannot be unsigned. Behaves like a CHAR column: "unpacked" means the number is stored as a string, using one character for each digit of the value, the decimal point, and, for negative numbers, the `-' sign. If D is 0, values will have no decimal point or fractional part. The maximum range of DECIMAL values is the same as for DOUBLE, but the actual range for a given DECIMAL column may be constrained by the choice of M and D. In MySQL 3.23 the M argument no longer includes the sign or the decimal point. (This is according to ANSI SQL.)

NUMERIC(M,D) [ZEROFILL]

This is a synonym for DECIMAL.

DATE

A date. The supported range is '1000-01-01' to '9999-12-31'. MySQL displays DATE values in 'YYYY-MM-DD' format, but allows you to assign values to DATE columns using either strings or numbers.

DATETIME

A date and time combination. The supported range is '1000-01-01 00:00:00' to '9999-12-31 23:59:59'. MySQL displays DATETIME values in 'YYYY-MM-DD HH:MM:SS' format, but allows you to assign values to DATETIME columns using either strings or numbers.

TIMESTAMP[(M)]

A timestamp. The range is '1970-01-01 00:00:00' to sometime in the year 2037. MySQL displays TIMESTAMP values in YYYYMMDDHHMMSS, YYMMDDHHMMSS, YYYYMMDD or YYMMDD format, depending on whether M is 14 (or missing), 12, 8 or 6, but allows you to assign values to TIMESTAMP columns using either strings or numbers. A TIMESTAMP column is useful for recording the date and time of an INSERT or UPDATE operation because it is automatically set to the date and time of the most recent operation if you don't give it a value yourself. You can also set it to the current date and time by assigning it a NULL value. See section 7.2.6 Date and time types.

TIME

A time. The range is '-838:59:59' to '838:59:59'. MySQL displays TIME values in 'HH:MM:SS' format, but allows you to assign values to TIME columns using either strings or numbers.

YEAR

A year. The allowable values are 1901 to 2155, and 0000. MySQL displays YEAR values in YYYY format, but allows you to assign values to YEAR columns using either strings or numbers. (The YEAR type is new in MySQL 3.22.)

CHAR(M) [BINARY]

A fixed-length string that is always right-padded with spaces to the specified length when stored. The range of M is 1 to 255 characters. Trailing spaces are removed when the value is retrieved. CHAR values are sorted and compared in case-insensitive fashion unless the BINARY keyword is given.

VARCHAR(M) [BINARY]

A variable-length string. Note: Trailing spaces are removed when the value is stored (this differs from the ANSI SQL specification). The range of M is 1 to 255 characters. VARCHAR values are sorted and compared in case-insensitive fashion unless the BINARY keyword is given. See section 7.6.1 Silent column specification changes.

TINYBLOB

TINYTEXT

A BLOB or TEXT column with a maximum length of 255 (2^8 - 1) characters. See section 7.6.1 Silent column specification changes.

BLOB

TEXT

A BLOB or TEXT column with a maximum length of 65535 (2^16 - 1) characters. See section 7.6.1 Silent column specification changes.

MEDIUMBLOB

MEDIUMTEXT

A BLOB or TEXT column with a maximum length of 16777215 (2^24 - 1) characters. See section 7.6.1 Silent column specification changes.

LONGBLOB

LONGTEXT

A BLOB or TEXT column with a maximum length of 4294967295 (2^32 - 1) characters. See section 7.6.1 Silent column specification changes.

ENUM('value1','value2',...)

An enumeration. A string object that can have only one value, chosen from the list of values 'value1', 'value2', ..., or NULL. An ENUM can have a maximum of 65535 distinct values.

SET('value1','value2',...)

A set. A string object that can have zero or more values, each of which must be chosen from the list of values 'value1', 'value2', ... A SET can have a maximum of 64 members.

7.2.1 Column type storage requirements

The storage requirements for each of the column types supported by MySQL are listed below by category.

7.2.2 Numeric types

7.2.3 Date and time types

7.2.4 String types

VARCHAR and the BLOB and TEXT types are variable-length types, for which the storage requirements depend on the actual length of column values (represented by L in the preceding table), rather than on the type's maximum possible size. For example, a VARCHAR(10) column can hold a string with a maximum length of 10 characters. The actual storage required is the length of the string (L), plus 1 byte to record the length of the string. For the string 'abcd', L is 4 and the storage requirement is 5 bytes.

The BLOB and TEXT types require 1, 2, 3 or 4 bytes to record the length of the column value, depending on the maximum possible length of the type.

If a table includes any variable-length column types, the record format will also be variable-length. Note that when a table is created, MySQL may under certain conditions change a column from a variable-length type to a fixed-length type, or vice-versa. See section 7.6.1 Silent column specification changes.

The size of an ENUM object is determined by the number of different enumeration values. 1 byte is used for enumerations with up to 255 possible values. 2 bytes are used for enumerations with up to 65535 values.

The size of a SET object is determined by the number of different set members. If the set size is N, the object occupies (N+7)/8 bytes, rounded up to 1, 2, 3, 4 or 8 bytes. A SET can have a maximum of 64 members.

7.2.5 Numeric types

All integer types can have an optional attribute UNSIGNED. Unsigned values can be used when you want to allow only positive numbers in a column and you need a little bigger numeric range for the column.

All numeric types can have an optional attribute ZEROFILL. Values for ZEROFILL columns are left-padded with zeroes up to the maximum display length when they are displayed. For example, for a column declared as INT(5) ZEROFILL, a value of 4 is retrieved as 00004.

When asked to store a value in a numeric column that is outside the column type's allowable range, MySQL clips the value to the appropriate endpoint of the range and stores the resulting value instead.

For example, the range of an INT column is -2147483648 to 2147483647. If you try to insert -9999999999 into an INT column, the value is clipped to the lower endpoint of the range, and -2147483648 is stored instead. Similarly, if you try to insert 9999999999, 2147483647 is stored instead.

If the INT column is UNSIGNED, the size of the column's range is the same but its endpoints shift up to 0 and 4294967295. If you try to store -9999999999 and 9999999999, the values stored in the column become 0 and 4294967296.

Conversions that occur due to clipping are reported as "warnings" for ALTER TABLE, LOAD DATA INFILE, UPDATE and multi-row INSERT statements.

The maximum display size (M) and number of decimals (D) are used for formatting and calculation of maximum column width.

MySQL will store any value that fits a column's storage type even if the value exceeds the display size. For example, an INT(4) column has a display size of 4. Suppose you insert a value which has more than 4 digits into the column, such as 12345. The display size is exceeded, but the allowable range of the INT type is not, so MySQL stores the actual value, 12345. When retrieving the value from the column, MySQL returns the actual value stored in the column. Note that if you store bigger values than the display width in a column, you may experience problems when MySQL generates temporary tables for some complicated joins as in these case MySQL trust that the data did fit into the original column width.

The DECIMAL type is considered a numeric type (as is its synonym, NUMERIC), but such values are stored as strings. One character is used for each digit of the value, the decimal point (if D > 0) and the `-' sign (for negative numbers). If D is 0, DECIMAL and NUMERIC values contain no decimal point or fractional part.

The maximum range of DECIMAL values is the same as for DOUBLE, but the actual range for a given DECIMAL column may be constrained by the choice of M and D. For example, a type specification such as DECIMAL(4,2) indicates a maximum length of four characters with two digits after the decimal point. Due to the way the DECIMAL type is stored, this specification results in an allowable range of -.99 to 9.99, much less than the range of a DOUBLE.

To avoid some rounding problems, MySQL always rounds everything that it stores in any floating-point column to the number of decimals indicated by the column specification. Suppose you have a column type of FLOAT(8,2). The number of decimals is 2, so a value such as 2.333 is rounded to two decimals and stored as 2.33.

7.2.6 Date and time types

The date and time types are DATETIME, DATE, TIMESTAMP, TIME and YEAR. Each of these has a range of legal values, as well as a "zero" value that is used when you specify an illegal value.

Here are some general considerations to keep in mind when working with date and time types:

• MySQL retrieves values for a given date or time type in a standard format, but it attempts to interpret a variety of formats for values that you supply (e.g., when you specify a value to be assigned to or compared to a date or time type). Nevertheless, only the formats described in the following sections are supported. It is expected that you will supply legal values, and unpredictable results may occur if you use values in other formats.
• Although MySQL tries to interpret values in several formats, it always expects the year part of date values to be leftmost. Dates must be given in year-month-day order (e.g., '98-09-04'), rather than in the month-day-year or day-month-year orders commonly used elsewhere (e.g., '09-04-98', '04-09-98').
• MySQL automatically converts a date or time type value to a number if the value is used in a numeric context, and vice versa.
• When MySQL encounters a value for a date or time type that is out of range or otherwise illegal for the type, it converts the value to the "zero" value for that type. (The exception is that out-of-range TIME values are clipped to the appropriate endpoint of the TIME range.) The table below shows the format of the "zero" value for each type:

  Column type	"Zero" value
  DATETIME	'0000-00-00 00:00:00'
  DATE	'0000-00-00'
  TIMESTAMP	00000000000000 (length depends on display size)
  TIME	'00:00:00'
  YEAR	0000

• The "zero" values are special, but you can store or refer to them explicitly using the values shown in the table. You can also do this using the values '0' or 0, which are easier to write.
• "Zero" date or time values used through MyODBC are converted automatically to NULL in MyODBC 2.50.12 and above, because ODBC can't handle such values.

7.2.6.1 Y2K issues and date types

MySQL itself is Y2K-safe (see section 1.6 Year 2000 compliance), but input values presented to MySQL may not be. Any input containing 2-digit year values is ambiguous, since the century is unknown. Such values must be interpreted into 4-digit form since MySQL stores years internally using four digits.

For DATETIME, DATE, TIMESTAMP and YEAR types, MySQL interprets dates with ambiguous year values using the following rules:

• Year values in the range 00-69 are converted to 2000-2069.
• Year values in the range 70-99 are converted to 1970-1999.

Remember that these rules provide only reasonable guesses as to what your data mean. If the heuristics used by MySQL don't produce the correct values, you should provide unambiguous input containing 4-digit year values.

7.2.6.2 The DATETIME, DATE and TIMESTAMP types

The DATETIME, DATE and TIMESTAMP types are related. This section describes their characteristics, how they are similar and how they differ.

The DATETIME type is used when you need values that contain both date and time information. MySQL retrieves and displays DATETIME values in 'YYYY-MM-DD HH:MM:SS' format. The supported range is '1000-01-01 00:00:00' to '9999-12-31 23:59:59'. ("Supported" means that although earlier values might work, there is no guarantee that they will.)

The DATE type is used when you need only a date value, without a time part. MySQL retrieves and displays DATE values in 'YYYY-MM-DD' format. The supported range is '1000-01-01' to '9999-12-31'.

The TIMESTAMP column type provides a type that you can use to automatically mark INSERT or UPDATE operations with the current date and time. If you have multiple TIMESTAMP columns, only the first one is updated automatically.

Automatic updating of the first TIMESTAMP column occurs under any of the following conditions:

• The column is not specified explicitly in an INSERT or LOAD DATA INFILE statement.
• The column is not specified explicitly in an UPDATE statement and some other column changes value. (Note that an UPDATE that sets a column to the value it already has will not cause the TIMESTAMP column to be updated, because if you set a column to its current value, MySQL ignores the update for efficiency.)
• You explicitly set the TIMESTAMP column to NULL.

TIMESTAMP columns other than the first may also be set to the current date and time. Just set the column to NULL, or to NOW().

You can set any TIMESTAMP column to a value different than the current date and time by setting it explicitly to the desired value. This is true even for the first TIMESTAMP column. You can use this property if, for example, you want a TIMESTAMP to be set to the current date and time when you create a row, but not to be changed whenever the row is updated later:

• Let MySQL set the column when the row is created. This will initialize it to the current date and time.
• When you perform subsequent updates to other columns in the row, set the TIMESTAMP column explicitly to its current value.

On the other hand, you may find it just as easy to use a DATETIME column that you initialize to NOW() when the row is created and leave alone for subsequent updates.

TIMESTAMP values may range from the beginning of 1970 to sometime in the year 2037, with a resolution of one second. Values are displayed as numbers.

The format in which MySQL retrieves and displays TIMESTAMP values depends on the display size, as illustrated by the table below. The `full' TIMESTAMP format is 14 digits, but TIMESTAMP columns may be created with shorter display sizes:

All TIMESTAMP columns have the same storage size, regardless of display size. The most common display sizes are 6, 8, 12, and 14. You can specify an arbitrary display size at table creation time, but values of 0 or greater than 14 are coerced to 14. Odd-valued sizes in the range from 1 to 13 are coerced to the next higher even number.

You can specify DATETIME, DATE and TIMESTAMP values using any of a common set of formats:

• As a string in either 'YYYY-MM-DD HH:MM:SS' or 'YY-MM-DD HH:MM:SS' format. A "relaxed" syntax is allowed--any punctuation character may be used as the delimiter between date parts or time parts. For example, '98-12-31 11:30:45', '98.12.31 11+30+45', '98/12/31 11*30*45' and '98@12@31 11^30^45' are equivalent.
• As a string in either 'YYYY-MM-DD' or 'YY-MM-DD' format. A "relaxed" syntax is allowed here, too. For example, '98-12-31', '98.12.31', '98/12/31' and '98@12@31' are equivalent.
• As a string with no delimiters in either 'YYYYMMDDHHMMSS' or 'YYMMDDHHMMSS' format, provided that the string makes sense as a date. For example, '19970523091528' and '970523091528' are interpreted as '1997-05-23 09:15:28', but '971122459015' is illegal (it has a nonsensical minute part) and becomes '0000-00-00 00:00:00'.
• As a string with no delimiters in either 'YYYYMMDD' or 'YYMMDD' format, provided that the string makes sense as a date. For example, '19970523' and '970523' are interpreted as '1997-05-23', but '971332' is illegal (it has nonsensical month and day parts) and becomes '0000-00-00'.
• As a number in either YYYYMMDDHHMMSS or YYMMDDHHMMSS format, provided that the number makes sense as a date. For example, 19830905132800 and 830905132800 are interpreted as '1983-09-05 13:28:00'.
• As a number in either YYYYMMDD or YYMMDD format, provided that the number makes sense as a date. For example, 19830905 and 830905 are interpreted as '1983-09-05'.
• As the result of a function that returns a value that is acceptable in a DATETIME, DATE or TIMESTAMP context, such as NOW() or CURRENT_DATE.

Illegal DATETIME, DATE or TIMESTAMP values are converted to the "zero" value of the appropriate type ('0000-00-00 00:00:00', '0000-00-00' or 00000000000000).

For values specified as strings that include date part delimiters, it is not necessary to specify two digits for month or day values that are less than 10. '1979-6-9' is the same as '1979-06-09'. Similarly, for values specified as strings that include time part delimiters, it is not necessary to specify two digits for hour, month or second values that are less than 10. '1979-10-30 1:2:3' is the same as '1979-10-30 01:02:03'.

Values specified as numbers should be 6, 8, 12 or 14 digits long. If the number is 8 or 14 digits long, it is assumed to be in YYYYMMDD or YYYYMMDDHHMMSS format and that the year is given by the first 4 digits. If the number is 6 or 12 digits long, it is assumed to be in YYMMDD or YYMMDDHHMMSS format and that the year is given by the first 2 digits. Numbers that are not one of these lengths are interpreted as though padded with leading zeros to the closest length.

Values specified as non-delimited strings are interpreted using their length as given. If the string is 8 or 14 characters long, the year is assumed to be given by the first 4 characters. Otherwise the year is assumed to be given by the first 2 characters. The string is interpreted from left to right to find year, month, day, hour, minute and second values, for as many parts as are present in the string. This means you should not use strings that have fewer than 6 characters. For example, if you specify '9903', thinking that will represent March, 1999, you will find that MySQL inserts a "zero" date into your table. This is because the year and month values are 99 and 03, but the day part is missing (zero), so the value is not a legal date.

TIMESTAMP columns store legal values using the full precision with which the value was specified, regardless of the display size. This has several implications:

• Always specify year, month, and day, even if your column types are TIMESTAMP(4) or TIMESTAMP(2). Otherwise, the value will not be a legal date and 0 will be stored.
• If you use ALTER TABLE to widen a narrow TIMESTAMP column, information will be displayed that previously was "hidden".
• Similarly, narrowing a TIMESTAMP column does not cause information to be lost, except in the sense that less information is shown when the values are displayed.
• Although TIMESTAMP values are stored to full precision, the only function that operates directly on the underlying stored value is UNIX_TIMESTAMP(). Other functions operate on the formatted retrieved value. This means you cannot use functions such as HOUR() or SECOND() unless the relevant part of the TIMESTAMP value is included in the formatted value. For example, the HH part of a TIMESTAMP column is not displayed unless the display size is at least 10, so trying to use HOUR() on shorter TIMESTAMP values produces a meaningless result.

You can to some extent assign values of one date type to an object of a different date type. However, there may be some alteration of the value or loss of information:

• If you assign a DATE value to a DATETIME or TIMESTAMP object, the time part of the resulting value is set to '00:00:00', because the DATE value contains no time information.
• If you assign a DATETIME or TIMESTAMP value to a DATE object, the time part of the resulting value is deleted, because the DATE type stores no time information.
• Remember that although DATETIME, DATE and TIMESTAMP values all can be specified using the same set of formats, the types do not all have the same range of values. For example, TIMESTAMP values cannot be earlier than 1970 or later than 2037. This means that a date such as '1968-01-01', while legal as a DATETIME or DATE value, is not a valid TIMESTAMP value and will be converted to 0 if assigned to such an object.

Be aware of certain pitfalls when specifying date values:

• The relaxed format allowed for values specified as strings can be deceiving. For example, a value such as '10:11:12' might look like a time value because of the `:' delimiter, but if used in a date context will be interpreted as the year '2010-11-12'. The value '10:45:15' will be converted to '0000-00-00' because '45' is not a legal month.
• Year values specified as two digits are ambiguous, since the century is unknown. MySQL interprets 2-digit year values using the following rules:
  • Year values in the range 00-69 are converted to 2000-2069.
  • Year values in the range 70-99 are converted to 1970-1999.

7.2.6.3 The TIME type

MySQL retrieves and displays TIME values in 'HH:MM:SS' format (or 'HHH:MM:SS' format for large hours values). TIME values may range from '-838:59:59' to '838:59:59'. The reason the hours part may be so large is that the TIME type may be used not only to represent a time of day (which must be less than 24 hours), but also elapsed time or a time interval between two events (which may be much greater than 24 hours, or even negative).

You can specify TIME values in a variety of formats:

• As a string in 'HH:MM:SS' format. A "relaxed" syntax is allowed--any punctuation character may be used as the delimiter between time parts. For example, '10:11:12' and '10.11.12' are equivalent.
• As a string with no delimiters in 'HHMMSS' format, provided that it makes sense as a time. For example, '101112' is understood as '10:11:12', but '109712' is illegal (it has a nonsensical minute part) and becomes '00:00:00'.
• As a number in HHMMSS format, provided that it makes sense as a time. For example, 101112 is understood as '10:11:12'.
• As the result of a function that returns a value that is acceptable in a TIME context, such as CURRENT_TIME.

For TIME values specified as strings that include a time part delimiter, it is not necessary to specify two digits for hours, minutes or seconds values that are less than 10. '8:3:2' is the same as '08:03:02'.

Be careful about assigning "short" TIME values to a TIME column. MySQL interprets values using the assumption that the rightmost digits represent seconds. (MySQL interprets TIME values as elapsed time, rather than as time of day.) For example, you might think of '11:12', '1112' and 1112 as meaning '11:12:00' (12 minutes after 11 o'clock), but MySQL interprets them as '00:11:12' (11 minutes, 12 seconds). Similarly, '12' and 12 are interpreted as '00:00:12'.

Values that lie outside the TIME range but are otherwise legal are clipped to the appropriate endpoint of the range. For example, '-850:00:00' and '850:00:00' are converted to '-838:59:59' and '838:59:59'.

Illegal TIME values are converted to '00:00:00'. Note that since '00:00:00' is itself a legal TIME value, there is no way to tell, from a value of '00:00:00' stored in a table, whether the original value was specified as '00:00:00' or whether it was illegal.

7.2.6.4 The YEAR type

The YEAR type is a 1-byte type used for representing years.

MySQL retrieves and displays YEAR values in YYYY format. The range is 1901 to 2155.

You can specify YEAR values in a variety of formats:

• As a four-digit string in the range '1901' to '2155'.
• As a four-digit number in the range 1901 to 2155.
• As a two-digit string in the range '00' to '99'. Values in the ranges '00' to '69' and '70' to '99' are converted to YEAR values in the ranges 2000 to 2069 and 1970 to 1999.
• As a two-digit number in the range 1 to 99. Values in the ranges 1 to 69 and 70 to 99 are converted to YEAR values in the ranges 2001 to 2069 and 1970 to 1999. Note that the range for two-digit numbers is slightly different than the range for two-digit strings, since you cannot specify zero directly as a number and have it be interpreted as 2000. You must specify it as a string '0' or '00' or it will be interpreted as 0000.
• As the result of a function that returns a value that is acceptable in a YEAR context, such as NOW().

Illegal YEAR values are converted to 0000.

7.2.7 String types

The string types are CHAR, VARCHAR, BLOB, TEXT, ENUM and SET.

7.2.7.1 The CHAR and VARCHAR types

The CHAR and VARCHAR types are similar, but differ in the way they are stored and retrieved.

The length of a CHAR column is fixed to the length that you declare when you create the table. The length can be any value between 1 and 255. (As of MySQL 3.23, the length of CHAR may be 0 to 255.) When CHAR values are stored, they are right-padded with spaces to the specified length. When CHAR values are retrieved, trailing spaces are removed.

Values in VARCHAR columns are variable-length strings. You can declare a VARCHAR column to be any length between 1 and 255, just as for CHAR columns. However, in contrast to CHAR, VARCHAR values are stored using only as many characters as are needed, plus one byte to record the length. Values are not padded; instead, trailing spaces are removed when values are stored. (This space removal differs from the ANSI SQL specification.)

If you assign a value to a CHAR or VARCHAR column that exceeds the column's maximum length, the value is truncated to fit.

The table below illustrates the differences between the two types of columns by showing the result of storing various string values into CHAR(4) and VARCHAR(4) columns:

The values retrieved from the CHAR(4) and VARCHAR(4) columns will be the same in each case, because trailing spaces are removed from CHAR columns upon retrieval.

Values in CHAR and VARCHAR columns are sorted and compared in case-insensitive fashion, unless the BINARY attribute was specified when the table was created. The BINARY attribute means that column values are sorted and compared in case-sensitive fashion according to the ASCII order of the machine where the MySQL server is running.

The BINARY attribute is "sticky". This means that if a column marked BINARY is used in an expression, the whole expression is compared as a BINARY value.

MySQL may silently change the type of a CHAR or VARCHAR column at table creation time. See section 7.6.1 Silent column specification changes.

7.2.7.2 The BLOB and TEXT types

A BLOB is a binary large object that can hold a variable amount of data. The four BLOB types TINYBLOB, BLOB, MEDIUMBLOB and LONGBLOB differ only in the maximum length of the values they can hold. See section 7.2.1 Column type storage requirements.

The four TEXT types TINYTEXT, TEXT, MEDIUMTEXT and LONGTEXT correspond to the four BLOB types and have the same maximum lengths and storage requirements. The only difference between BLOB and TEXT types is that sorting and comparison is performed in case-sensitive fashion for BLOB values and case-insensitive fashion for TEXT values. In other words, a TEXT is a case-insensitive BLOB.

If you assign a value to a BLOB or TEXT column that exceeds the column type's maximum length, the value is truncated to fit.

In most respects, you can regard a TEXT column as a VARCHAR column that can be as big as you like. Similarly, you can regard a BLOB column as a VARCHAR BINARY column. The differences are:

• You can have indexes on BLOB and TEXT columns with MySQL versions 3.23.2 and newer. Older versions of MySQL did not support this.
• There is no trailing-space removal for BLOB and TEXT columns when values are stored, as there is for VARCHAR columns.
• BLOB and TEXT columns cannot have DEFAULT values.

MyODBC defines BLOB values as LONGVARBINARY and TEXT values as LONGVARCHAR.

Because BLOB and TEXT values may be extremely long, you may run up against some constraints when using them:

• If you want to use GROUP BY or ORDER BY on a BLOB or TEXT column, you must convert the column value into a fixed-length object. The standard way to do this is with the SUBSTRING function. For example:

  mysql> select comment from tbl_name,substring(comment,20) as substr ORDER BY substr;
  

  If you don't do this, only the first max_sort_length bytes of the column are used when sorting. The default value of max_sort_length is 1024; this value can be changed using the -O option when starting the mysqld server. You can group on an expression involving BLOB or TEXT values by specifying the column position or by using an alias:

  mysql> select id,substring(blob_col,1,100) from tbl_name
             GROUP BY 2;
  mysql> select id,substring(blob_col,1,100) as b from tbl_name
             GROUP BY b;
  

• The maximum size of a BLOB or TEXT object is determined by its type, but the largest value you can actually transmit between the client and server is determined by the amount of available memory and the size of the communications buffers. You can change the message buffer size, but you must do so on both the server and client ends. See section 10.1 Tuning server parameters.

Note that each BLOB or TEXT value is represented internally by a separately-allocated object. This is in contrast to all other column types, for which storage is allocated once per column when the table is opened.

7.2.7.3 The ENUM type

An ENUM is a string object whose value normally is chosen from a list of allowed values that are enumerated explicitly in the column specification at table creation time.

The value may also be the empty string ("") or NULL under certain circumstances:

• If you insert an invalid value into an ENUM (that is, a string not present in the list of allowed values), the empty string is inserted instead as a special error value.
• If an ENUM is declared NULL, NULL is also a legal value for the column, and the default value is NULL. If an ENUM is declared NOT NULL, the default value is the first element of the list of allowed values.

Each enumeration value has an index:

• Values from the list of allowable elements in the column specification are numbered beginning with 1.
• The index value of the empty string error value is 0. This means that you can use the following SELECT statement to find rows into which invalid ENUM values were assigned:

  mysql> SELECT * FROM tbl_name WHERE enum_col=0;
  

• The index of the NULL value is NULL.

For example, a column specified as ENUM("one", "two", "three") can have any of the values shown below. The index of each value is also shown: