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, “SQL:2003” refers to the standard released in 2003, and “SQL:2008” refers to the most recent version of the standard, released in 2008. 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.
HANDLER interface is an example
of this strategy. See Section 13.2.4, “HANDLER Syntax”.
We continue to support transactional and nontransactional 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.
We are not targeting real-time support, although MySQL replication capabilities offer significant functionality.
MySQL supports ODBC levels 0 to 3.51.
MySQL supports high-availability database clustering using the
NDBCLUSTER storage engine. See
Chapter 18, MySQL NDB Cluster 7.3 and NDB Cluster 7.4.
We implement XML functionality which supports most of the W3C XPath standard. See Section 12.11, “XML Functions”.
The MySQL server can operate in different SQL modes, and can apply
these modes differently for different clients, depending on the
value of the
variable. DBAs can set the global SQL mode to match site server
operating requirements, and each application can set its session
SQL mode to its own requirements.
Modes affect the SQL syntax MySQL supports and the data validation checks it performs. This makes it easier to use MySQL in different environments and to use MySQL together with other database servers.
For more information on setting the SQL mode, see Section 5.1.8, “Server SQL Modes”.
To achieve the same effect at runtime, execute 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'