MyISAM

MyISAM (My Indexed Sequential Access Method) is a storage engine of database management system MySQL. It is built to complement some extensions on the older ISAM system and was until MySQL 5.1 default storage engine. Since version 5.5 it was replaced by InnoDB as the default storage engine.

Properties

MyISAM is characterized by high efficiency compared to other supported by MySQL Table Types and since 3.23.23 of MySQL supports a powerful full- text search. MyISAM is next recommended for tables that are read much more often is (SELECT), as it is written in ( INSERT / UPDATE). However, MyISAM supports in contrast to, for example, InnoDB no transactions, so that in the event of a fault may remain inconsistent data in the database if some have already been carried out by several related queries and not others. Also, MyISAM does not provide referential integrity.

For each MyISAM table three files are created in the file system. The names of each of the files consist of the name of the table and a file name extension that identifies the file type: . Frm For the table definition for which data MYD ( MyData ) and for the index MYI ( MyIndex ). ..

To explicitly create a MyISAM table, the ENGINE option can be specified in SQL:

CREATE TABLE t (i INT) ENGINE = MYISAM; (Note: Older versions of MySQL using the TYPE keyword instead ENGINE (example: TYPE = MYISAM ) MySQL 5.0 and 5.1 support this syntax backwards compatible, but the use of ENGINE is recommended since MySQL 5.5 is only supported the keyword ENGINE. .. )

The use of ENGINE is optional. If not specified, stored in the Preferences table type will be used. MySQL InnoDB uses by default since version 5.5.