Storage Engines

MySQL 524 's storage engines are pluggable: each table names its engine in ENGINE= (Table Options), and one query may join tables that use different engines. SHOW ENGINES lists what the server offers; the same data in information_schema.ENGINES lets you pick columns and rows:

SELECT engine, support, transactions, xa, savepoints
FROM information_schema.ENGINES WHERE support <> 'NO' ORDER BY engine;

+--------------------+---------+--------------+------+------------+
| engine             | support | transactions | xa   | savepoints |
+--------------------+---------+--------------+------+------------+
| ARCHIVE            | YES     | NO           | NO   | NO         |
| BLACKHOLE          | YES     | NO           | NO   | NO         |
| CSV                | YES     | NO           | NO   | NO         |
| InnoDB             | DEFAULT | YES          | YES  | YES        |
| MEMORY             | YES     | NO           | NO   | NO         |
| MRG_MYISAM         | YES     | NO           | NO   | NO         |
| MyISAM             | YES     | NO           | NO   | NO         |
| PERFORMANCE_SCHEMA | YES     | NO           | NO   | NO         |
+--------------------+---------+--------------+------+------------+
8 rows in set (0.000 sec)

Only InnoDB supports transactions, XA and savepoints; FEDERATED (remote tables) and NDB (MySQL Cluster) are present but disabled. The others have narrow uses:

MyISAM ignores transactions: in a test run, a MyISAM INSERT survived ROLLBACK, which warned "Some non-transactional changed tables couldn't be rolled back" (1196). MEMORY tables are capped by max_heap_table_size (16 MB by default). ARCHIVE compresses rows and refuses UPDATE and DELETE, CSV stores a comma-separated file, and BLACKHOLE discards rows but still writes the binary log. ALTER TABLE t ENGINE = InnoDB converts an old table by rebuilding it.