MyISAM is the default storage engine as of MySQL 3.23. It is based on the ISAM code but has many useful extensions.
Each MyISAM table is stored on disk in three files. The files have names that begin with the table name and have an extension to indicate the file type. An .frm file stores the table format. The data file has an .MYD (MYData) extension. The index file has an .MYI (MYIndex) extension.
To specify explicitly that you want a MyISAM table, indicate that with an ENGINE table option:
CREATE TABLE t (i INT) ENGINE = MYISAM;
1.1.1.3Merge
The MERGE storage engine, also known as the MRG_MyISAM engine, is a collection of identical MyISAM tables that can be used as one. "Identical" means that all tables have identical column and index information.
You cannot merge MyISAM tables in which the columns are listed in a different order, do not have exactly the same columns, or have the indexes in different order. However, any or all of the My-ISAM tables can be compressed with myisampack. See Section 8.5, "myisampack - Generate Compressed, Read-Only MyISAM Tables". Differences in table options such as AVG_ROW_LENGTH,
MAX_ROWS, or PACK_KEYS do not matter.
1.1.1.4InnoDB
InnoDB provides MySQL with a transaction-safe (ACID compliant) storage engine that has commit,
rollback, and crash recovery capabilities. InnoDB does locking on the row level and also provides an Oracle-style consistent non-locking read in SELECT statements. These features increase multi-user concurrency
and performance. There is no need for lock escalation in InnoDB because row-level locks fit in very little space. InnoDB also supports FOREIGN KEY constraints. You can freely mix InnoDB tables with tables from other MySQL storage engines, even within the same statement.