7. ENGINES
ENGINES表提供有关存储引擎的信息。 这对于检查是否支持存储引擎或查看默认引擎是什么特别有用。
| INFORMATION_SCHEMA Name | SHOW Name |
|---|---|
| ENGINE | Engine |
| SUPPORT | Support |
| COMMENT | Comment |
| TRANSACTIONS | Transactions |
| XA | XA |
| SAVEPOINTS | Savepoints |
ENGINES表有以下列：
- ENGINE：存储引擎名称
- SUPPORT：服务器对存储引擎的支持级别，如下表所示。
| 值 | 含义 |
|---|---|
| YES | 引擎受支持且处于活动状态 |
| DEFAULT | 类似YES，并且表示是默认引擎 |
| NO | 不支持引擎 |
| DISABLED | 引擎受支持但已被禁用 |
值NO表示编译服务器时不支持引擎，因此无法在运行时启用它。
出现DISABLED值的原因是服务器是使用禁用引擎的选项启动的，或者因为没有给出启用它所需的所有选项。 在后一种情况下，错误日志应包含指示禁用该选项的原因。 请参见第“错误日志”。
如果服务器已编译为支持存储引擎，您可能还会看到DISABLED，但是使用--skip-engine_name选项启动。 对于NDB存储引擎，DISABLED表示服务器是在支持NDB Cluster的情况下编译的，但未使用--ndbcluster选项启动。
所有MySQL服务器都支持MyISAM表。 无法禁用MyISAM。
- COMMENT：存储引擎的简要说明。
- TRANSACTIONS：存储引擎是否支持XA事务。
- SAVEPOINTS：存储引擎是否支持保存点。
该ENGINES表是一个非标准INFORMATION_SCHEMA表。
mysql> select * from information_schema.engines;
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| ENGINE | SUPPORT | COMMENT | TRANSACTIONS | XA | SAVEPOINTS |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| CSV | YES | CSV storage engine | NO | NO | NO |
| MRG_MYISAM | YES | Collection of identical MyISAM tables | NO | NO | NO |
| MyISAM | YES | MyISAM storage engine | NO | NO | NO |
| BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) | NO | NO | NO |
| PERFORMANCE_SCHEMA | YES | Performance Schema | NO | NO | NO |
| MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO |
| ARCHIVE | YES | Archive storage engine | NO | NO | NO |
| InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES | YES | YES |
| FEDERATED | NO | Federated MySQL storage engine | NULL | NULL | NULL |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
9 rows in set (0.00 sec)
mysql> show engines;
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| Engine | Support | Comment | Transactions | XA | Savepoints |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| CSV | YES | CSV storage engine | NO | NO | NO |
| MRG_MYISAM | YES | Collection of identical MyISAM tables | NO | NO | NO |
| MyISAM | YES | MyISAM storage engine | NO | NO | NO |
| BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) | NO | NO | NO |
| PERFORMANCE_SCHEMA | YES | Performance Schema | NO | NO | NO |
| MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO |
| ARCHIVE | YES | Archive storage engine | NO | NO | NO |
| InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES | YES | YES |
| FEDERATED | NO | Federated MySQL storage engine | NULL | NULL | NULL |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
9 rows in set (0.01 sec)