Table of Contents
The MySQL® software delivers a very fast, multi-threaded, multi-user, and robust SQL (Structured Query Language) database server. MySQL Server is intended for mission-critical, heavy-load production systems as well as for embedding into mass-deployed software. MySQL is a registered trademark of MySQL AB.
The MySQL software is Dual Licensed. Users can choose to use the MySQL software as an Open Source product under the terms of the GNU General Public License (http://www.fsf.org/licenses/) or can purchase a standard commercial license from MySQL AB. See http://www.mysql.com/company/legal/licensing/ for more information on our licensing policies.
The following list describes some sections of particular interest in this manual:
For a discussion about the capabilities of the MySQL Database Server, see Section 1.4.3, “The Main Features of MySQL”.
For future plans, see Section 1.6, “MySQL Development Roadmap”.
For installation instructions, see Chapter 2, Installing and Upgrading MySQL. For information about upgrading MySQL, see Section 2.11, “Upgrading MySQL”.
For a tutorial introduction to the MySQL Database Server, see Chapter 3, Tutorial.
For information about configuring and administering MySQL Server, see Chapter 5, Database Administration.
For information about setting up replication servers, see Chapter 15, Replication.
For answers to a number of questions that are often asked concerning the MySQL Database Server and its capabilities, see Appendix A, MySQL 5.1 Frequently Asked Questions.
For a list of currently known bugs and misfeatures, see Section B.1.8, “Known Issues in MySQL”.
For a list of all the contributors to this project, see Appendix E, Credits.
For a history of new features and bugfixes, see Appendix C, MySQL Change History.
For tips on porting the MySQL Database Software to new architectures or operating systems, see MySQL Internals: Porting.
For benchmarking information, see the
sql-bench benchmarking directory in your
MySQL distribution.
To report errors (often called “bugs”), please use the instructions at Section 1.8, “How to Report Bugs or Problems”.
If you have found a sensitive security bug in MySQL Server, please
let us know immediately by sending an email message to
<security@mysql.com>.
This is the Reference Manual for the MySQL Database System,
version 5.1, through release 5.1.21-beta. It is
not intended for use with older versions of the MySQL software due
to the many functional and other differences between MySQL
5.1 and previous versions. If you are using an
earlier release of the MySQL software, please refer to the
MySQL 5.0 Reference Manual,
which covers the 5.0 series of MySQL software
releases, or to
MySQL 3.23, 4.0,
4.1 Reference Manual, which covers the 3.23,
4.0, and 4.1 series of MySQL software releases. Differences
between minor versions of MySQL 5.1 are noted in the
present text with reference to release numbers
(5.1.x).
Because this manual serves as a reference, it does not provide general instruction on SQL or relational database concepts. It also does not teach you how to use your operating system or command-line interpreter.
The MySQL Database Software is under constant development, and the Reference Manual is updated frequently as well. The most recent version of the manual is available online in searchable form at http://dev.mysql.com/doc/. Other formats also are available there, including HTML, PDF, and Windows CHM versions.
The Reference Manual source files are written in DocBook XML format. The HTML version and other formats are produced automatically, primarily using the DocBook XSL stylesheets. For information about DocBook, see http://docbook.org/
The DocBook XML sources of this manual are available from http://dev.mysql.com/tech-resources/sources.html. You can check out a copy of the documentation repository with this command:
svn checkout http://svn.mysql.com/svnpublic/mysqldoc/
If you have questions about using MySQL, you can ask them using
our mailing lists or forums. See Section 1.7.1, “MySQL Mailing Lists”,
and Section 1.7.2, “MySQL Community Support at the MySQL Forums”. If you have suggestions concerning
additions or corrections to the manual itself, please send them to
the documentation team at <docs@mysql.com>.
This manual was originally written by David Axmark and Michael “Monty” Widenius. It is maintained by the MySQL Documentation Team, consisting of Paul DuBois, Stefan Hinz, Jon Stephens, Martin MC Brown, and Peter Lavin. For the many other contributors, see Appendix E, Credits.
The copyright to this manual is owned by the Swedish company MySQL AB. MySQL® and the MySQL logo are registered trademarks of MySQL AB. Other trademarks and registered trademarks referred to in this manual are the property of their respective owners, and are used for identification purposes only.
This manual uses certain typographical conventions:
Text in this style is used for SQL
statements; database, table, and column names; program listings
and source code; and environment variables. Example: “To
reload the grant tables, use the FLUSH
PRIVILEGES statement.”
Text in this style indicates input that
you type in examples.
Text in this style indicates the names of executable programs and scripts, examples being mysql (the MySQL command line client program) and mysqld (the MySQL server executable).
Text in this style is used for
variable input for which you should substitute a value of your
own choosing.
Filenames and directory names are written like this: “The
global my.cnf file is located in the
/etc directory.”
Character sequences are written like this: “To specify a
wildcard, use the ‘%’
character.”
Text in this style is used for emphasis.
Text in this style is used in table headings and to convey especially strong emphasis.
When commands are shown that are meant to be executed from within a
particular program, the prompt shown preceding the command indicates
which command to use. For example, shell>
indicates a command that you execute from your login shell, and
mysql> indicates a statement that you execute
from the mysql client program:
shell>type a shell command heremysql>type a mysql statement here
The “shell” is your command interpreter. On Unix, this is typically a program such as sh, csh, or bash. On Windows, the equivalent program is command.com or cmd.exe, typically run in a console window.
When you enter a command or statement shown in an example, do not type the prompt shown in the example.
Database, table, and column names must often be substituted into
statements. 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 keywords are not case sensitive and may be written in any lettercase. This manual uses uppercase.
In syntax descriptions, square brackets
(‘[’ and
‘]’) indicate optional words or
clauses. For example, in the following statement, IF
EXISTS is optional:
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 (‘[’
and ‘]’):
TRIM([[BOTH | LEADING | TRAILING] [remstr] FROM]str)
When one member from a set of choices must be
chosen, the alternatives are listed within braces
(‘{’ and
‘}’):
{DESCRIBE | DESC} tbl_name [col_name | wild]
An ellipsis (...) indicates the omission of a
section of a statement, typically to provide a shorter version of
more complex syntax. For example, INSERT ...
SELECT is shorthand for the form of
INSERT statement that is followed by a
SELECT statement.
An ellipsis can also indicate that the preceding syntax element of a
statement may be repeated. In the following example, multiple
reset_option values may be given, with
each of those after the first preceded by commas:
RESETreset_option[,reset_option] ...
Commands for setting shell variables are shown using Bourne shell
syntax. For example, the sequence to set the CC
environment variable and run the configure
command looks like this in Bourne shell syntax:
shell> CC=gcc ./configure
If you are using csh or tcsh, you must issue commands somewhat differently:
shell>setenv CC gccshell>./configure
MySQL AB is the company of the MySQL founders and main developers. MySQL AB was originally established in Sweden by David Axmark, Allan Larsson, and Michael “Monty” Widenius.
We are dedicated to developing the MySQL database software and promoting it to new users. MySQL AB owns the copyright to the MySQL source code, the MySQL logo and (registered) trademark, and this manual. See Section 1.4, “Overview of the MySQL Database Management System”.
The MySQL core values show our dedication to MySQL and Open Source.
These core values direct how MySQL AB works with the MySQL server software:
To be the best and the most widely used database in the world
To be available and affordable by all
To be easy to use
To be continuously improved while remaining fast and safe
To be fun to use and improve
To be free from bugs
These are the core values of the company MySQL AB and its employees:
We subscribe to the Open Source philosophy and support the Open Source community
We aim to be good citizens
We prefer partners that share our values and mindset
We answer email and provide support
We are a virtual company, networking with others
We work against software patents
The MySQL Web site (http://www.mysql.com/) provides the latest information about MySQL and MySQL AB.
By the way, the “AB” part of the company name is the acronym for the Swedish “aktiebolag,” or “stock company.” It translates to “MySQL, Inc.” In fact, MySQL, Inc. and MySQL GmbH are examples of MySQL AB subsidiaries. They are located in the United States and Germany, respectively.
MySQL, the most popular Open Source SQL database management system, is developed, distributed, and supported by MySQL AB. MySQL AB is a commercial company, founded by the MySQL developers. It is a second generation Open Source company that unites Open Source values and methodology with a successful business model.
The MySQL Web site (http://www.mysql.com/) provides the latest information about MySQL software and MySQL AB.
MySQL is a database management system.
A database is a structured collection of data. It may be anything from a simple shopping list to a picture gallery or the vast amounts of information in a corporate network. To add, access, and process data stored in a computer database, you need a database management system such as MySQL Server. Since computers are very good at handling large amounts of data, database management systems play a central role in computing, as standalone utilities, or as parts of other applications.
MySQL is a relational database management system.
A relational database stores data in separate tables rather than putting all the data in one big storeroom. This adds speed and flexibility. The SQL part of “MySQL” stands for “Structured Query Language.” SQL is the most common standardized language used to access databases and is defined by the ANSI/ISO SQL Standard. The SQL standard has been evolving since 1986 and several versions exist. In this manual, “SQL-92” refers to the standard released in 1992, “SQL:1999” refers to the standard released in 1999, and “SQL:2003” refers to the current version of the standard. We use the phrase “the SQL standard” to mean the current version of the SQL Standard at any time.
MySQL software is Open Source.
Open Source means that it is possible for anyone to use and modify the software. Anybody can download the MySQL software from the Internet and use it without paying anything. If you wish, you may study the source code and change it to suit your needs. The MySQL software uses the GPL (GNU General Public License), http://www.fsf.org/licenses/, to define what you may and may not do with the software in different situations. If you feel uncomfortable with the GPL or need to embed MySQL code into a commercial application, you can buy a commercially licensed version from us. See the MySQL Licensing Overview for more information (http://www.mysql.com/company/legal/licensing/).
The MySQL Database Server is very fast, reliable, and easy to use.
If that is what you are looking for, you should give it a try. MySQL Server also has a practical set of features developed in close cooperation with our users. You can find a performance comparison of MySQL Server with other database managers on our benchmark page. See Section 6.1.4, “The MySQL Benchmark Suite”.
MySQL Server was originally developed to handle large databases much faster than existing solutions and has been successfully used in highly demanding production environments for several years. Although under constant development, MySQL Server today offers a rich and useful set of functions. Its connectivity, speed, and security make MySQL Server highly suited for accessing databases on the Internet.
MySQL Server works in client/server or embedded systems.
The MySQL Database Software is a client/server system that consists of a multi-threaded SQL server that supports different backends, several different client programs and libraries, administrative tools, and a wide range of application programming interfaces (APIs).
We also provide MySQL Server as an embedded multi-threaded library that you can link into your application to get a smaller, faster, easier-to-manage standalone product.
A large amount of contributed MySQL software is available.
It is very likely that your favorite application or language supports the MySQL Database Server.
The official way to pronounce “MySQL” is “My Ess Que Ell” (not “my sequel”), but we don't mind if you pronounce it as “my sequel” or in some other localized way.
We started out with the intention of using the
mSQL database system 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
designed to allow third-party code that was written for use with
mSQL to be ported easily for use with MySQL.
MySQL is named after co-founder Monty Widenius's daughter, My.
The name of the MySQL Dolphin (our logo) is “Sakila,” which was chosen by the founders of MySQL AB from a huge list of names suggested by users in our “Name the Dolphin” contest. The winning name was submitted by Ambrose Twebaze, an Open Source software developer from Swaziland, Africa. According to Ambrose, the feminine name Sakila has its roots in SiSwati, the local language of Swaziland. Sakila is also the name of a town in Arusha, Tanzania, near Ambrose's country of origin, Uganda.
This section describes some of the important characteristics of the MySQL Database Software. See also Section 1.6, “MySQL Development Roadmap”, for more information about current and upcoming features. In most respects, it applies to all versions of MySQL. For information about features as they are introduced into MySQL on a series-specific basis, see the “In a Nutshell” section of the appropriate Manual:
MySQL 4.0 and 4.1: MySQL 4.0 in a Nutshell, and MySQL 4.1 in a Nutshell.
MySQL 5.0: MySQL 5.0 in a Nutshell.
MySQL 5.1: MySQL 5.1 in a Nutshell.
Internals and Portability:
Written in C and C++.
Tested with a broad range of different compilers.
Works on many different platforms. See Section 2.1.1, “Operating Systems Supported by MySQL Community Server”.
Uses GNU Automake, Autoconf, and Libtool for portability.
The MySQL Server design is multi-layered with independent modules.
Fully multi-threaded using kernel threads. It can easily use multiple CPUs if they are available.
Provides transactional and non-transactional storage engines.
Uses very fast B-tree disk tables (MyISAM)
with index compression.
Relatively easy to add other storage engines. This is useful if you want to provide an SQL interface for an in-house database.
A very fast thread-based memory allocation system.
Very fast joins using an optimized one-sweep multi-join.
In-memory hash tables, which are used as temporary tables.
SQL functions are implemented using a highly optimized class library and should be as fast as possible. Usually there is no memory allocation at all after query initialization.
The MySQL code is tested with Purify (a commercial memory leakage detector) as well as with Valgrind, a GPL tool (http://developer.kde.org/~sewardj/).
The server is available as a separate program for use in a client/server networked environment. It is also available as a library that can be embedded (linked) into standalone applications. Such applications can be used in isolation or in environments where no network is available.
Data Types:
Many data types: signed/unsigned integers 1, 2, 3, 4, and 8
bytes long, FLOAT,
DOUBLE, CHAR,
VARCHAR, TEXT,
BLOB, DATE,
TIME, DATETIME,
TIMESTAMP, YEAR,
SET, ENUM, and OpenGIS
spatial types. See Chapter 10, Data Types.
Fixed-length and variable-length records.
Statements and Functions:
Full operator and function support in the
SELECT list and WHERE
clause of queries. For example:
mysql>SELECT CONCAT(first_name, ' ', last_name)->FROM citizen->WHERE income/dependents > 10000 AND age > 30;
Full support for SQL GROUP BY and
ORDER BY clauses. Support for group
functions (COUNT(), COUNT(DISTINCT
...), AVG(),
STD(), SUM(),
MAX(), MIN(), and
GROUP_CONCAT()).
Support for LEFT OUTER JOIN and
RIGHT OUTER JOIN with both standard SQL and
ODBC syntax.
Support for aliases on tables and columns as required by standard SQL.
DELETE, INSERT,
REPLACE, and UPDATE
return the number of rows that were changed (affected). It is
possible to return the number of rows matched instead by
setting a flag when connecting to the server.
The MySQL-specific SHOW statement can be
used to retrieve information about databases, storage engines,
tables, and indexes. MySQL 5.0 adds support for the
INFORMATION_SCHEMA database, implemented
according to standard SQL.
The EXPLAIN statement can be used to
determine how the optimizer resolves a query.
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 8.3, “Reserved Words”.
You can refer to tables from different databases in the same statement.
Security:
A privilege and password system that is very flexible and secure, and that allows host-based verification.
Passwords are secure because all password traffic is encrypted when you connect to a server.
Scalability and Limits:
Handles large databases. We use MySQL Server with databases that contain 50 million records. We also know of users who use MySQL Server with 60,000 tables and about 5,000,000,000 rows.
Up to 64 indexes per table are allowed (32 before MySQL
4.1.2). Each index may consist of 1 to 16 columns or parts of
columns. The maximum index width is 1000 bytes (767 for
InnoDB); before MySQL 4.1.2, the limit is
500 bytes. An index may use a prefix of a column for
CHAR, VARCHAR,
BLOB, or TEXT column
types.
Connectivity:
Clients can connect to MySQL Server using several protocols:
Clients can connect using TCP/IP sockets on any platform.
On Windows systems in the NT family (NT, 2000, XP, 2003,
or Vista), clients can connect using named pipes if the
server is started with the
--enable-named-pipe option. In MySQL 4.1
and higher, Windows servers also support shared-memory
connections if started with the
--shared-memory option. Clients can
connect through shared memory by using the
--protocol=memory option.
On Unix systems, clients can connect using Unix domain socket files.
MySQL client programs can be written in many languages. A client library written in C is available for clients written in C or C++, or for any language that provides C bindings.
APIs for C, C++, Eiffel, Java, Perl, PHP, Python, Ruby, and Tcl are available, allowing MySQL clients to be written in many languages. See Chapter 25, APIs and Libraries.
The Connector/ODBC (MyODBC) interface provides MySQL support for client programs that use ODBC (Open Database Connectivity) connections. For example, you can use MS Access to connect to your MySQL server. Clients can be run on Windows or Unix. MyODBC source is available. All ODBC 2.5 functions are supported, as are many others. See Chapter 26, Connectors.
The Connector/J interface provides MySQL support for Java client programs that use JDBC connections. Clients can be run on Windows or Unix. Connector/J source is available. See Chapter 26, Connectors.
MySQL Connector/NET enables developers to easily create .NET applications that require secure, high-performance data connectivity with MySQL. It implements the required ADO.NET interfaces and integrates into ADO.NET aware tools. Developers can build applications using their choice of .NET languages. MySQL Connector/NET is a fully managed ADO.NET driver written in 100% pure C#. See Chapter 26, Connectors.
Localization:
The server can provide error messages to clients in many languages. See Section 5.10.2, “Setting the Error Message Language”.
Full support for several different character sets, including
latin1 (cp1252), german,
big5, ujis, and more.
For example, the Scandinavian characters
‘å’,
‘ä’ and
‘ö’ are allowed in table and
column names. Unicode support is available as of MySQL 4.1.
All data is saved in the chosen character set.
Sorting and comparisons are done according to the chosen
character set and collation (using latin1
and Swedish collation by default). It is possible to change
this when the MySQL server is started. To see an example of
very advanced sorting, look at the Czech sorting code. MySQL
Server supports many different character sets that can be
specified at compile time and runtime.
As of MySQL 4.1, the server time zone can be changed dynamically, and individual clients can specify their own time zone. Section 5.10.8, “MySQL Server Time Zone Support”.
MySQL Enterprise For assistance in getting optimal performance from your MySQL server subscribe to MySQL Enterprise. For more information see http://www.mysql.com/products/enterprise/.
Clients and Tools:
MySQL AB provides several client and utility programs. These include both command-line programs such as mysqldump and mysqladmin, and graphical programs such as MySQL Administrator and MySQL Query Browser.
MySQL Server has built-in support for SQL statements to check,
optimize, and repair tables. These statements are available
from the command line through the
mysqlcheck client. MySQL also includes
myisamchk, a very fast command-line utility
for performing these operations on MyISAM
tables. See Chapter 7, Client and Utility Programs.
MySQL programs can be invoked with the --help
or -? option to obtain online assistance.
MaxDB is a heavy-duty enterprise database. The database management system is SAP-certified.
MaxDB is the new name of a database management system formerly called SAP DB. In 2003 SAP AG and MySQL AB joined a partnership and re-branded the database system to MaxDB. The development of MaxDB has continued since then as it was done before—through the SAP developer team.
MySQL AB cooperates closely with the MaxDB team at SAP around delivering improvements to the MaxDB product. Joint efforts include development of new native drivers to enable more efficient usage of MaxDB in the Open Source community, and improvement of documentation to expand the MaxDB user base. Interoperability features between MySQL and MaxDB database also are seen as important. For example, the new MaxDB Synchronization Manager supports data synchronization from MaxDB to MySQL.
The MaxDB database management system does not share a common code-base with the MySQL database management system. The MaxDB and MySQL database management systems are independent products provided by MySQL AB.
MySQL AB offers a complete portfolio of Professional Services for MaxDB.
MaxDB is an ANSI SQL-92 (entry level) compliant relational database management system (RDBMS) from SAP AG, that is delivered by MySQL AB as well. MaxDB fulfills the needs for enterprise usage: safety, scalability, high concurrency, and performance. It runs on all major operating systems. Over the years it has proven able to run SAP R/3 and terabytes of data in 24×7 operation.
The database development started in 1977 as a research project at the Technical University of Berlin. In the early 1980s it became a database product that subsequently was owned by Nixdorf, Siemens Nixdorf, Software AG, and today by SAP AG. Along the way, it has been named VDN, Reflex, Supra 2, DDB/4, Entire SQL-DB-Server, and ADABAS D. In 1997, SAP took over the software from Software AG and renamed it to SAP DB. Since October 2000, SAP DB sources additionally were released as Open Source under the GNU General Public License (see GNU General Public License).
In 2003, SAP AG and MySQL AB formed a partnership and re-branded the database system to MaxDB.
The history of MaxDB goes back to SAP DB, SAP AG's DBMS. That is, MaxDB is a re-branded and enhanced version of SAP DB. For many years, MaxDB has been used for small, medium, and large installations of the mySAP Business Suite and other demanding SQL applications requiring an enterprise-class DBMS with regard to the number of users, the transactional workload, and the size of the database.
SAP DB was meant to provide an alternative to third-party database systems such as Oracle, Microsoft SQL Server, and DB2 by IBM. In October 2000, SAP AG released SAP DB under the GNU GPL license (see GNU General Public License), thus making it Open Source software.
Today, MaxDB is used in about 3,500 SAP customer installations worldwide. Moreover, the majority of all DBMS installations on Unix and Linux within SAP’s IT department rely on MaxDB. MaxDB is tuned toward heavy-duty online transaction processing (OLTP) with several thousand users and database sizes ranging from several hundred GB to multiple TB.
In 2003, SAP and MySQL concluded a partnership and development cooperation agreement. As a result, SAP's database system SAP DB has been delivered under the name of MaxDB by MySQL since the release of version 7.5 (November 2003).
Version 7.5 of MaxDB is a direct advancement of the SAP DB 7.4 code base. Therefore, the MaxDB software version 7.5 can be used as a direct upgrade of previous SAP DB versions starting 7.2.04 and higher.
The former SAP DB development team at SAP AG is responsible, now as before, for developing and supporting MaxDB. MySQL AB cooperates closely with the MaxDB team at SAP around delivering improvements to the MaxDB product, see Section 1.5, “Overview of the MaxDB Database Management System”. Both SAP AG and MySQL AB handle the sale and distribution of MaxDB. The advancement of MaxDB and the MySQL Server leverages synergies that benefit both product lines.
MaxDB is subjected to SAP AG's complete quality assurance process before it is shipped with SAP solutions or provided as a download from the MySQL site.
MaxDB is a heavy-duty, SAP-certified Open Source database for OLTP and OLAP usage which offers high reliability, availability, scalability, and a very comprehensive feature set. It is targeted for large mySAP Business Suite environments and other applications that require maximum enterprise-level database functionality and complements the MySQL database server.
MaxDB operates as a client/server product. It was developed to meet the needs of installations in OLTP and Data Warehouse/OLAP/Decision Support scenarios and offers these benefits:
Easy configuration and administration: GUI-based Installation Manager and Database Manager as single administration tools for DBMS operations
Around-the-clock operation, no planned downtimes, no permanent attendance required: Automatic space management, no need for reorganizations
Sophisticated backup and restore capabilities: Online and incremental backups, recovery wizard to guide you through the recovery scenario
Supports large number of users, database sizes in the terabytes, and demanding workloads: Proven reliability, performance, and scalability
High availability: Cluster support, standby configuration, hot standby configuration
MaxDB can be used under the same licenses available for the other products distributed by MySQL AB. Thus, MaxDB is available under the GNU General Public License, and a commercial license. For more information on licensing, see http://www.mysql.com/company/legal/licensing/.
MySQL AB offers MaxDB technical support to non-SAP customers. MaxDB support is available on various levels (Basic, Silver, and Gold), which expand from unlimited email/web-support to 24×7 phone support for business critical systems.
MySQL AB also offers Licenses and Support for MaxDB when used with SAP Applications, like SAP NetWeaver and mySAP Business Suite. For more information on licenses and support for your needs, please contact MySQL AB. (See http://www.mysql.com/company/contact/.)
Consulting and training services are available. MySQL gives classes on MaxDB at regular intervals. See http://www.mysql.com/training/ for a list of classes.
MaxDB is MySQL AB's SAP-certified database. The MaxDB database server complements the MySQL AB product portfolio. Some MaxDB features are not available on the MySQL database management server and vice versa.
The following list summarizes the main differences between MaxDB and MySQL; it is not complete.
MaxDB runs as a client/server system. MySQL can run as a client/server system or as an embedded system.
MaxDB might not run on all platforms supported by MySQL.
MaxDB uses a proprietary network protocol for client/server communication. MySQL uses either TCP/IP (with or without SSL encryption), sockets (under Unix-like systems), or named pipes or shared memory (under Windows NT-family systems).
MaxDB supports stored procedures and functions. MySQL 5.0 and up also supports stored procedures and functions. MaxDB supports programming of triggers through an SQL extension. MySQL 5.0 supports triggers. MaxDB contains a debugger for stored procedure languages, can cascade nested triggers, and supports multiple triggers per action and row.
MaxDB is distributed with user interfaces that are text-based, graphical, or Web-based. MySQL is distributed with text-based user interfaces only; graphical user interfaces such as MySQL Query Browser or MySQL Administrator are shipped separately from the main distributions. Web-based user interfaces for MySQL are offered by third parties.
MaxDB supports a number of programming interfaces that also are supported by MySQL. For developing with MaxDB, the MaxDB ODBC Driver, SQL Database Connectivity (SQLDBC), JDBC Driver, Perl and Python modules and a MaxDB PHP extension, which provides access to MySQL MaxDB databases using PHP, are available. Third Party Programming Interfaces: Support for OLE DB, ADO, DAO, RDO and .NET through ODBC. MaxDB supports embedded SQL with C/C++.
MaxDB includes administrative features that MySQL does not have: job scheduling by time (included in MySQL as of 5.1), event, and alert, and sending messages to a database administrator on alert thresholds. (MySQL has scheduling support starting with version 5.1.6.)
MaxDB and MySQL are independent database management servers. The interoperation of the systems is possible in a way that the systems can exchange their data. To exchange data between MaxDB and MySQL, you can use the import and export tools of the systems or the MaxDB Synchronization Manager. The import and export tools can be used to transfer data in an infrequent, manual fashion. The MaxDB Synchronization Manager offers faster, automatic data transfer capabilities.
The MaxDB Loader can be used to export data and object
definitions. The Loader can export data using MaxDB internal,
binary formats and text formats (CSV). Data exported from MaxDB in
text formats can be imported into MySQL using the
mysqlimport client program. To export MySQL
data, you can use either mysqldump to create
INSERT statements or SELECT ... INTO
OUTFILE to create a text file (CSV). Use the MaxDB
Loader to import the data files generated by MySQL.
Object definitions can be exchanged between the systems using
MaxDB Loader and the MySQL tool mysqldump. As
the SQL dialects of both systems differ slightly and MaxDB has
features currently not supported by MySQL like SQL constraints, we
recommend to hand-tune the definition files. The
mysqldump tool offers an option
--compatible=maxdb to produce output that is
compatible with MaxDB to make porting easier.
The MaxDB Synchronization Manager is available as part of MaxDB 7.6. The Synchronization Manager supports creation of asynchronous replication scenarios between several MaxDB instances. However, interoperability features also are planned, so that the Synchronization Manager supports replication to and from a MySQL server.
The main page for MaxDB information is http://www.mysql.com/products/maxdb, which provides details about the features of the MaxDB database management systems and has pointers to available documentation.
The MySQL Reference Manual does not contain any MaxDB documentation other than the introduction given in this section. MaxDB has its own documentation, which is called the MaxDB library and is available at http://dev.mysql.com/doc/maxdb/index.html.
MySQL AB runs a community mailing list on MaxDB; see http://lists.mysql.com/maxdb. The list shows a vivid community discussion. Many of the core developers contribute to it. Product announcements are sent to the list.
A Web forum on MaxDB is available at http://forums.mysql.com/. The forum focuses on MaxDB questions not related to SAP applications.
This section describes the general MySQL development roadmap, provides an overview about features that have been implemented in previous series and that are new in this current release series (5.1), and an overview about upcoming additions or changes in the next release series (5.2).
The maturity level of the release series covered in this manual (5.1) is beta. Information about maturity levels can be found in Section 2.1.2.1, “Choosing Which Version of MySQL to Install”.
Before upgrading from one release series to the next, please see the notes in Section 2.11, “Upgrading MySQL”.
The most requested features and the versions in which they were implemented or are scheduled for implementation are summarized in the following table:
| Feature | MySQL Series |
| Unions | 4.0 |
| Subqueries | 4.1 |
| R-trees | 4.1 (for the MyISAM storage engine) |
| Stored procedures | 5.0 |
| Views | 5.0 |
| Cursors | 5.0 |
| XA transactions | 5.0 |
| Triggers | 5.0 and 5.1 |
| Event scheduler | 5.1 |
| Partitioning | 5.1 |
| Pluggable storage engine API | 5.1 |
| Plugin API | 5.1 |
| Row-based replication | 5.1 |
| Server log tables | 5.1 |
| Foreign keys | 5.2 (implemented in 3.23 for InnoDB) |
The following features have been added to MySQL 5.1.
Partitioning: This
capability enables distributing portions of individual
tables across a filesystem, according to rules which can be
set when the table is created. In effect, different portions
of a table are stored as separate tables in different
locations, but from the user point of view, the partitioned
table is still a single table. Syntactically, this
implements a number of new extensions to the CREATE
TABLE, ALTER TABLE, and
EXPLAIN ... SELECT statements. As of
MySQL 5.1.6, queries against partitioned tables can take
advantage of partition pruning. In some
cases, this can result in query execution that is an order
of magnitude faster than the same query against a
non-partitioned version of the same table. See
Chapter 17, Partitioning, for further information on
this functionality. (Author: Mikael Ronström)
Row-based replication: Replication capabilities in MySQL originally were based on propagation of SQL statements from master to slave. This is called statement-based replication. As of MySQL 5.1.5, another basis for replication is available. This is called row-based replication. Instead of sending SQL statements to the slave, the master writes events to its binary log that indicate how individual table rows are effected. As of MySQL 5.1.8, a third option is available: mixed. This will use statement-based replication by default, and only switch to row-based replication in particular cases. See Section 15.1.2, “Replication Formats”. (Authors: Lars Thalmann, Guilhem Bichot, Mats Kindahl)
Plugin API: MySQL 5.1 adds support for a very flexible plugin API that enables loading and unloading of various components at runtime, without restarting the server. Although the work on this is not finished yet, plugin full-text parsers are a first step in this direction. This allows users to implement their own input filter on the indexed text, enabling full-text search capability on arbitrary data such as PDF files or other document formats. A pre-parser full-text plugin performs the actual parsing and extraction of the text and hands it over to the built-in MySQL full-text search. See Section 28.2, “The MySQL Plugin Interface”. (Author: Sergey Vojtovich)
Event scheduler: MySQL
Events are tasks that run according to a schedule. When you
create an event, you are creating a named database object
containing one or more SQL statements to be executed at one
or more regular intervals, beginning and ending at a
specific date and time. Conceptually, this is similar to the
idea of the Unix crontab (also known as a
“cron job”) or the Windows Task Scheduler. See
Chapter 21, Event Scheduler. (Author: Andrey Hristov)
Server log tables: Before
MySQL 5.1, the server writes general query log and slow
query log entries to log files. As of MySQL 5.1, the
server's logging capabilities for these logs are more
flexible. Log entries can be written to log files (as
before) or to the general_log and
slow_log tables in the
mysql database. If logging is enabled,
either or both destinations can be selected. The
--log-output option controls the
destination or destinations of log output. See
Section 5.11.1, “Selecting General Query and Slow Query Log Output Destinations”. (Author: Petr Chardin)
The Instance Manager (IM)
now has some additional functionality: SHOW
provides a listing of all log files, instance_name LOG FILESSHOW
retrieves
a part of the specified log file, and instance_name LOG {ERROR | SLOW |
GENERAL} sizeSET
sets an option to the specified value and writes it to the
configuration file. See Section 5.4, “mysqlmanager — The MySQL Instance Manager”.
(Author: Petr Chardin)
instance_name.option_name=option_value
Upgrade program: The mysql_upgrade program (available as of MySQL 5.1.7) checks all existing tables for incompatibilities with the current version of MySQL Server and repairs them if necessary. This program should be run for each MySQL upgrade. See Section 5.5.7, “mysql_upgrade — Check Tables for MySQL Upgrade”. (Authors: Alexey Botchkov, Mikael Widenius)
Replication between MySQL Clusters is now supported. It is now also possible to replicate between a MySQL Cluster and a non-cluster database. See Section 16.10, “MySQL Cluster Replication”.
MySQL Cluster Disk Data: In
MySQL versions previous to 5.1.6, the
NDBCluster storage engine was strictly
in-memory; beginning with MySQL 5.1.6, it is possible to
store Cluster data (but not indexes) on disk. This allows
MySQL Cluster to scale upward with fewer hardware (RAM)
requirements than previously. See
Section 16.11, “MySQL Cluster Disk Data Tables”.
The Disk Data implementation includes a new “no-steal” restoration algorithm for fast node restarts when storing very large amounts of data (terabyte range).
Online ADD INDEX
and DROP INDEX for MySQL
Cluster: Adding and dropping indexes is now much
faster for tables using the NDB storage
engine than in previous versions of MySQL Cluster. This is
due to the fact that NDB no longer needs
to re-create tables, but instead can now apply these schema
changes directly to existing tables.
Improved backup implementation in MySQL Cluster: A fault arising in a single data node during a Cluster backup no longer causes the entire backup to be aborted, as occurred in previous versions of MySQL Cluster.
Backup of tablespaces: The
mysqldump utility now supports an option
for dumping tablespaces. Use -Y or
--all-tablespaces to enable this
functionality.
Improvements to
INFORMATION_SCHEMA: MySQL 5.1
provides much more information in its metadata database. New
tables in that database include FILES,
EVENTS, PARTITIONS,
PROCESSLIST, ENGINES,
and PLUGINS.
XML functions:
ExtractValue() returns the content of a
fragment of XML matching a given XPath expression.
UpdateXML() replaces the element selected
from a fragment of XML by an XPath expression supplied by
the user with a second XML fragment (also user-supplied),
and returns the modified XML. See
Section 11.10, “XML Functions”. (Author: Alexander Barkov)
Load emulator: The mysqlslap program is designed to emulate client load for a MySQL server and report the timing of each stage. It works as if multiple clients were accessing the server. See Section 7.17, “mysqlslap — Load Emulation Client”. (Authors: Patrick Galbraith, Brian Aker)
This section is subject to change as long as MySQL 5.2 development is in its early stages.
The following features will be added to MySQL 5.2, or change in MySQL 5.2.
RESET SLAVE no longer changes replication
connection parameters. Previously, it reset them to the
values specified on the command line.
The following constructs are deprecated and have been removed in MySQL 5.2. Where alternatives are shown, applications should be updated to use them.
The table_type system variable (use
storage_engine)
The log_bin_trust_routine_creators
variable (use
log_bin_trust_function_creators)
TIMESTAMP(:
The ability to specify a display width of
N)N (use without
N)
The TYPE table option to specify the
storage engine for CREATE TABLE or
ALTER TABLE (use
ENGINE)
The SHOW TABLE TYPES SQL statement (use
SHOW ENGINES)
The SHOW INNODB STATUS SQL statement (use
SHOW ENGINE INNODB STATUS)
The SHOW MUTEX STATUS SQL statement (use
SHOW ENGINE INNODB MUTEX)
The LOAD TABLE ... FROM MASTER and
LOAD DATA FROM MASTER SQL statements
The SHOW PLUGIN SQL statement (use
SHOW PLUGINS)
The RESTORE TABLE SQL statement
The BACKUP TABLE SQL statement
The --master-
server options to set replication parameters (use the
xxxCHANGE MASTER statement)
This section lists sources of additional information that you may find helpful, such as the MySQL mailing lists and user forums, and Internet Relay Chat.
This section introduces the MySQL mailing lists and provides guidelines as to how the lists should be used. When you subscribe to a mailing list, you receive all postings to the list as email messages. You can also send your own questions and answers to the list.
To subscribe to or unsubscribe from any of the mailing lists described in this section, visit http://lists.mysql.com/. For most of them, you can select the regular version of the list where you get individual messages, or a digest version where you get one large message per day.
Please do not send messages about subscribing or unsubscribing to any of the mailing lists, because such messages are distributed automatically to thousands of other users.
Your local site may have many subscribers to a MySQL mailing list.
If so, the site 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.
If you wish to have traffic for a mailing list go to a separate
mailbox in your mail program, set up a filter based on the message
headers. You can use either the List-ID: or
Delivered-To: headers to identify list
messages.
The MySQL mailing lists are as follows:
announce
This list is for announcements of new versions of MySQL and related programs. This is a low-volume list to which all MySQL users should subscribe.
mysql
This is 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.
bugs
This list is for people who want to stay informed about issues reported since the last release of MySQL or who want to be actively involved in the process of bug hunting and fixing. See Section 1.8, “How to Report Bugs or Problems”.
internals
This list is for people who work on the MySQL code. This is also the forum for discussions on MySQL development and for posting patches.
mysqldoc
This list is for people who work on the MySQL documentation: people from MySQL AB, translators, and other community members.
benchmarks
This list is for anyone interested in performance issues. Discussions concentrate on database performance (not limited to MySQL), but also include broader categories such as performance of the kernel, filesystem, disk system, and so on.
packagers
This list is for discussions on packaging and distributing MySQL. This is the forum used by distribution maintainers to exchange ideas on packaging MySQL and on ensuring that MySQL looks and feels as similar as possible on all supported platforms and operating systems.
java
This list is for discussions about the MySQL server and Java. It is mostly used to discuss JDBC drivers such as MySQL Connector/J.
win32
This list is for all topics concerning the MySQL software on Microsoft operating systems, such as Windows 9x, Me, NT, 2000, XP, and 2003.
myodbc
This list is for all topics concerning connecting to the MySQL server with ODBC.
gui-tools
This list is for all topics concerning MySQL graphical user
interface tools such as MySQL Administrator
and MySQL Query Browser.
cluster
This list is for discussion of MySQL Cluster.
dotnet
This list is for discussion of the MySQL server and the .NET platform. It is mostly related to MySQL Connector/Net.
plusplus
This list is for all topics concerning programming with the C++ API for MySQL.
perl
This list is for all topics concerning Perl support for MySQL
with DBD::mysql.
If you're unable to get an answer to your questions from a MySQL mailing list or forum, one option is to purchase support from MySQL AB. This puts you in direct contact with MySQL developers.
The following table shows some MySQL mailing lists in languages other than English. These lists are not operated by MySQL AB.
<mysql-france-subscribe@yahoogroups.com>
A French mailing list.
A Korean mailing list. To subscribe, email subscribe
mysql your@email.address to this list.
<mysql-de-request@lists.4t2.com>
A German mailing list. To subscribe, email subscribe
mysql-de your@email.address to this list. You can
find information about this mailing list at
http://www.4t2.com/mysql/.
<mysql-br-request@listas.linkway.com.br>
A Portuguese mailing list. To subscribe, email
subscribe mysql-br your@email.address to
this list.
A Spanish mailing list. To subscribe, email subscribe
mysql your@email.address to this list.
Please don't post mail messages from your browser with HTML mode turned on. Many users don't read mail with a browser.
When you answer a question sent to a mailing list, if you consider your answer to have broad interest, you may want to post it to the 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.
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.
The forums at http://forums.mysql.com are an important community resource. Many forums are available, grouped into these general categories:
Migration
MySQL Usage
MySQL Connectors
Programming Languages
Tools
3rd-Party Applications
Storage Engines
MySQL Technology
SQL Standards
Business
In addition to the various MySQL mailing lists and forums, you can find experienced community people on Internet Relay Chat (IRC). These are the best networks/channels currently known to us:
freenode (see http://www.freenode.net/ for servers)
#mysql is primarily for MySQL questions,
but other database and general SQL questions are welcome.
Questions about PHP, Perl, or C in combination with MySQL are
also common.
If you are looking for IRC client software to connect to an IRC
network, take a look at xChat
(http://www.xchat.org/). X-Chat (GPL licensed) is
available for Unix as well as for Windows platforms (a free
Windows build of X-Chat is available at
http://www.silverex.org/download/).
MySQL AB offers technical support in the form of MySQL Enterprise. For organizations that rely on the MySQL DBMS for business-critical production applications, MySQL Enterprise is a commercial subscription offering which includes:
MySQL Enterprise Server
MySQL Enterprise Monitor
Monthly Rapid Updates and Quarterly Service Packs
MySQL Knowledge Base
24x7 Technical and Consultative Support
MySQL Enterprise is available in multiple tiers, giving you the flexibility to choose the level of service that best matches your needs. For more information see MySQL Enterprise.
Before posting a bug report about a problem, please try to verify that it is a bug and that it has not been reported already:
Start by searching the MySQL online manual at http://dev.mysql.com/doc/. We try to keep the manual up to date by updating it frequently with solutions to newly found problems. The change history (http://dev.mysql.com/doc/mysql/en/news.html) can be particularly useful since it is quite possible that a newer version contains a solution to your problem.
If you get a parse error for a SQL statement, please check your
syntax closely. If you can't find something wrong with it, it's
extremely likely that your current version of MySQL Server
doesn't support the syntax you are using. If you are using the
current version and the manual doesn't cover the syntax that you
are using, MySQL Server doesn't support your statement. In this
case, your options are to implement the syntax yourself or email
<licensing@mysql.com> and ask for an offer to
implement it.
If the manual covers the syntax you are using, but you have an older version of MySQL Server, you should check the MySQL change history to see when the syntax was implemented. In this case, you have the option of upgrading to a newer version of MySQL Server.
For solutions to some common problems, see Section B.1, “Problems and Common Errors”.
Search the bugs database at http://bugs.mysql.com/ to see whether the bug has been reported and fixed.
Search the MySQL mailing list archives at http://lists.mysql.com/. See Section 1.7.1, “MySQL Mailing Lists”.
You can also use http://www.mysql.com/search/ to search all the Web pages (including the manual) that are located at the MySQL AB Web site.
If you can't find an answer in the manual, the bugs database, or the mailing list archives, check with your local MySQL expert. If you still can't find an answer to your question, please use the following guidelines for reporting the bug.
The normal way to report bugs is to visit http://bugs.mysql.com/, which is the address for our bugs database. This database is public and can be browsed and searched by anyone. If you log in to the system, you can enter new reports. If you have no Web access, you can generate a bug report by using the mysqlbug script described at the end of this section.
Bugs posted in the bugs database at http://bugs.mysql.com/ that are corrected for a given release are noted in the change history.
If you have found a sensitive security bug in MySQL, you can send
email to <security@mysql.com>.
To discuss problems with other users, you can use one of the MySQL mailing lists. Section 1.7.1, “MySQL Mailing Lists”.
Writing a good bug report takes patience, but doing it right the first time saves time both for us and for yourself. A good bug report, containing a full test case for the bug, makes it very likely that we will fix the bug in the next release. This section helps you write your report correctly so that you don't waste your time doing things that may not help us much or at all. Please read this section carefully and make sure that all the information described here is included in your report.
Preferably, you should test the problem using the latest production
or development version of MySQL Server before posting. Anyone should
be able to repeat the bug by just using mysql test <
script_file on your test case or by running the shell or
Perl script that you include in the bug report. Any bug that we are
able to repeat has a high chance of being fixed in the next MySQL
release.
It is most helpful when a good description of the problem is included in the bug report. That is, give a good example of everything you did that led to the problem and describe, in exact detail, the problem itself. The best reports are those that include a full example showing how to reproduce the bug or problem. See MySQL Internals: Porting.
Remember that it is possible for us to respond to a report containing too much information, but not to one containing too little. People often omit facts because they think they know the cause of a problem and assume that some details don't matter. A good principle to follow is that if you are in doubt about stating something, state it. It is faster and less troublesome to write a couple more lines in your report than to wait longer for the answer if we must ask you to provide information that was missing from the initial report.
The most common errors made in bug reports are (a) not including the version number of the MySQL distribution that you use, and (b) not fully describing the platform on which the MySQL server is installed (including the platform type and version number). These are highly relevant pieces of information, and in 99 cases out of 100, the bug report is useless without them. Very often we get questions like, “Why doesn't this work for me?” 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 in newer MySQL versions. Errors often are platform-dependent. In such cases, it is next to impossible for us to fix anything without knowing the operating system and the version number of the platform.
If you compiled MySQL from source, 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. To determine whether your problem depends on your compiler, we need to know what compiler you used. Note that every compiling problem should be regarded as a bug and reported accordingly.
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, it is better that the error message reported exactly matches the one that the program produces. (Even the lettercase should be observed.) It is best to copy and paste the entire error message into your report. You should never try to reproduce the message from memory.
If you have a problem with Connector/ODBC (MyODBC), please try to generate a trace file and send it with your report. See the MyODBC section of Chapter 26, Connectors.
If your report includes long query output lines from test cases that
you run with the mysql command-line tool, you can
make the output more readable by using the
--vertical option or the \G
statement terminator. The EXPLAIN SELECT example
later in this section demonstrates the use of \G.
Please include the following information in your report:
The version number of the MySQL distribution you are using (for
example, MySQL 5.0.19). You can find out which version you are
running by executing mysqladmin version. The
mysqladmin program can be found in the
bin directory under your MySQL installation
directory.
The manufacturer and model of the machine on which you experience the problem.
The operating system name and version. If you work with Windows,
you can usually get the name and version number by
double-clicking your My Computer icon and pulling down the
“Help/About Windows” menu. For most Unix-like
operating systems, you can get this information by executing the
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 the MySQL software, include the name and version number of the compiler that you used. If you have a binary distribution, include the distribution name.
If the problem occurs during compilation, include the exact error messages and also a few lines of context around the offending code in the file where the error occurs.
If mysqld died, you should also report the statement that crashed mysqld. You can usually get this information by running mysqld with query logging enabled, and then looking in the log after mysqld crashes. See MySQL Internals: Porting.
If a database table is related to the problem, include the
output from the SHOW CREATE TABLE
statement in the bug report. This is a very easy way to get the
definition of any table in a database. The information helps us
create a situation matching the one that you have experienced.
db_name.tbl_name
The SQL mode in effect when the problem occurred can be
significant, so please report the value of the
sql_mode system variable. For stored
procedure, stored function, and trigger objects, the relevant
sql_mode value is the one in effect when the
object was created. For a stored procedure or function, the
SHOW CREATE PROCEDURE or SHOW CREATE
FUNCTION statement shows the relevant SQL mode, or you
can query INFORMATION_SCHEMA for the
information:
SELECT ROUTINE_SCHEMA, ROUTINE_NAME, SQL_MODE FROM INFORMATION_SCHEMA.ROUTINES;
For triggers, you can use this statement:
SELECT EVENT_OBJECT_SCHEMA, EVENT_OBJECT_TABLE, TRIGGER_NAME, SQL_MODE FROM INFORMATION_SCHEMA.TRIGGERS;
For performance-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. You should also include the output from
SHOW CREATE TABLE
for each table
that is involved. The more information you provide about your
situation, the more likely it is that someone can help you.
tbl_name
The following is an example of a very good bug report. The
statements are run using the mysql
command-line tool. Note the use of the \G
statement terminator for statements that would otherwise provide
very long output lines that are difficult to read.
mysql>SHOW VARIABLES;mysql>SHOW COLUMNS FROM ...\G<output from SHOW COLUMNS>mysql>EXPLAIN SELECT ...\G<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 mysqld, try to provide an input script that reproduces the anomaly. This script should include any necessary source files. The more closely the script can reproduce your situation, the better. If you can make a reproducible test case, you should upload it to be attached to the bug report.
If you can't provide a script, you should at least include the output from mysqladmin variables extended-status processlist in your report to provide some information on how your system is performing.
If you can't produce a test case with only a few rows, or if the
test table is too big to be included in the bug report (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://ftp.mysql.com/pub/mysql/upload/. Then enter the problem into
our bugs database at http://bugs.mysql.com/.
If you believe that the MySQL server produces a strange result from a statement, include not only the result, but also your opinion of what the result should be, and an explanation describing the basis for your opinion.
When you provide an example of the problem, it's better to use the table names, variable names, and so forth that exist in your actual situation than to come up with new names. The problem could be related to the name of a table or variable. 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. If you have data that you don't want to be visible to others in the bug report, you can use FTP to transfer it to ftp://ftp.mysql.com/pub/mysql/upload/. If the information is really top secret and you don't want to show it even to us, 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 server, as well as the
options that you use to run any MySQL client programs. The
options to programs such as mysqld and
mysql, and to the
configure script, are often key to resolving
problems and are very relevant. It is never a bad idea to
include them. If your problem involves a program written in a
language such as Perl or PHP, please include the language
processor's version number, as well as the version for any
modules that the program uses. For example, if you have a Perl
script that uses the DBI and
DBD::mysql modules, include the version
numbers for Perl, DBI, and
DBD::mysql.
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 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, do include it. But don't assume that the patch is all we need, or that we can use it, 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 the exact purpose of the patch, we won't use it. Test cases help us here. Show that the patch handles all the situations that may occur. If we find a borderline case (even a rare one) where the patch won't work, it may be useless.
Guesses about what the bug is, why it occurs, or what it depends on are usually wrong. Even the MySQL team can't guess such things without first using a debugger to determine the real cause of a bug.
Indicate in your bug report that you have checked the reference manual and mail archive so that others know you have tried to solve the problem yourself.
If the problem is that your data appears corrupt or you get
errors when you access a particular table, you should first
check your tables and then try to repair them with
CHECK TABLE and REPAIR
TABLE or with myisamchk. See
Chapter 5, Database Administration.
If you are running Windows, please verify the value of
lower_case_table_names using the
SHOW VARIABLES LIKE 'lower_case_table_names'
command. This variable affects how the server handles lettercase
of database and table names. Its effect for a given value should
be as described in
Section 8.2.2, “Identifier Case Sensitivity”.
If you often get corrupted tables, you should try to find out
when and why this happens. In this case, the error log in the
MySQL data directory may contain some information about what
happened. (This is the file with the .err
suffix in the name.) See Section 5.11.2, “The Error Log”. 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 cause of
mysqld dying, it's much easier for us to
provide you with a fix for the problem. See
Section B.1.1, “How to Determine What Is Causing a Problem”.
If possible, download and install the most recent version of MySQL Server and check whether it solves your problem. All versions of the MySQL software 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 without difficulty. See Section 2.1.2, “Choosing Which MySQL Distribution to Install”.
If you have no Web access and cannot report a bug by visiting
http://bugs.mysql.com/, you can use the
mysqlbug script to generate a bug report (or a
report about any problem). mysqlbug 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. mysqlbug can be found in
the scripts directory (source distribution) and
in the bin directory under your MySQL
installation directory (binary distribution).
This section describes how MySQL relates to the ANSI/ISO SQL standards. MySQL Server has many extensions to the SQL standard, and here you can find out what they are and how to use them. You can also find information about functionality missing from MySQL Server, and how to work around some of the differences.
The SQL standard has been evolving since 1986 and several versions exist. In this manual, “SQL-92” refers to the standard released in 1992, “SQL:1999” refers to the standard released in 1999, and “SQL:2003” refers to the current version of the standard. We use the phrase “the SQL standard” or “standard SQL” to mean the current version of the SQL Standard at any time.
One of our main goals with the product is to continue to work
toward compliance with the SQL standard, but without sacrificing
speed or reliability. We are not afraid to add extensions to SQL
or support for non-SQL features if this greatly increases the
usability of MySQL Server for a large segment of our user base.
The HANDLER interface is an example of this
strategy. See Section 12.2.3, “HANDLER Syntax”.
We continue to support transactional and non-transactional databases to satisfy both mission-critical 24/7 usage and heavy Web or logging usage.
MySQL Server was originally designed to work with medium-sized databases (10-100 million rows, or about 100MB per table) on small computer systems. Today MySQL Server handles terabyte-sized databases, but the code can also be compiled in a reduced version suitable for hand-held and embedded devices. The compact design of the MySQL server makes development in both directions possible without any conflicts in the source tree.
Currently, we are not targeting real-time support, although MySQL replication capabilities offer significant functionality.
MySQL supports high-availability database clustering using the
NDBCluster storage engine. See
Chapter 16, MySQL Cluster.
We are implementing XML functionality beginning in MySQL 5.1, which supports most of the W3C XPath standard. We plan to increase support for XML as part of future MySQL development. See Section 11.10, “XML Functions”.
Our aim is to support the full ANSI/ISO SQL standard, but without making concessions to speed and quality of the code.
ODBC levels 0-3.51.
The MySQL server can operate in different SQL modes, and can apply these modes differentially for different clients. This capability enables each application to tailor the server's operating mode to its own requirements.
SQL modes control aspects of server operation such as what SQL syntax MySQL should support and what kind of data validation checks it should perform. This makes it easier to use MySQL in different environments and to use MySQL together with other database servers.
You can set the default SQL mode by starting
mysqld with the
--sql-mode="
option. You can also change the mode at runtime by setting the
mode_value"sql_mode system variable with a SET
[SESSION|GLOBAL]
sql_mode='
statement.
mode_value'
For more information on setting the SQL mode, see Section 5.2.6, “SQL Modes”.
You can tell mysqld to run in ANSI mode with
the --ansi startup option. Running the server
in ANSI mode is the same as starting it with the following
options:
--transaction-isolation=SERIALIZABLE --sql-mode=ANSI
You can achieve the same effect at runtime by executing these two statements:
SET GLOBAL TRANSACTION ISOLATION LEVEL SERIALIZABLE; SET GLOBAL sql_mode = 'ANSI';
You can see that setting the sql_mode system
variable to 'ANSI' enables all SQL mode
options that are relevant for ANSI mode as follows:
mysql>SET GLOBAL sql_mode='ANSI';mysql>SELECT @@global.sql_mode;-> 'REAL_AS_FLOAT,PIPES_AS_CONCAT,ANSI_QUOTES,IGNORE_SPACE,ANSI'
Note that running the server in ANSI mode with
--ansi is not quite the same as setting the SQL
mode to 'ANSI'. The --ansi
option affects the SQL mode and also sets the transaction
isolation level. Setting the SQL mode to
'ANSI' has no effect on the isolation level.
See Section 5.2.2, “Command Options”, and Section 1.9.2, “Selecting SQL Modes”.
MySQL Server supports some extensions that you probably won't find in other SQL DBMSs. Be warned that if you use them, your code won't 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 following form:
/*! MySQL-specific code */
In this case, MySQL Server parses and executes the code within the comment as it would any other SQL statement, but other SQL