因为MySQL默认的是MyISAM数据引擎，不支持事务也不支持外键，所以需要用到Innodb引擎，于是决定将mysql的默认引擎设置为innodb。

1 . 查看MySQL存储引擎是用的哪个？登录MySQL数据库，在mysql>提示符下搞入show engines;命令。
+------------+---------+----------------------------------------------------------------+
| Engine     | Support | Comment                                                        |
+------------+---------+----------------------------------------------------------------+
| MyISAM     | DEFAULT | Default engine as of MySQL 3.23 with great performance         |
| MEMORY     | YES     | Hash based, stored in memory, useful for temporary tables      |
| InnoDB     | YES     | Supports transactions, row-level locking, and foreign keys     |
| BerkeleyDB | YES     | Supports transactions and page-level locking                   |
| BLACKHOLE  | NO      | /dev/null storage engine (anything you write to it disappears) |
| EXAMPLE    | NO      | Example storage engine                                         |
| ARCHIVE    | NO      | Archive storage engine                                         |
| CSV        | NO      | CSV storage engine                                             |
| ndbcluster | NO      | Clustered, fault-tolerant, memory-based tables                 |
| FEDERATED  | NO      | Federated MySQL storage engine                                 |
| MRG_MYISAM | YES     | Collection of identical MyISAM tables                          |
| ISAM       | NO      | Obsolete storage engine                                        |
+------------+---------+----------------------------------------------------------------+

说明目前默认的数据引擎是MyISAM，并且也支持InnoDB引擎。

2. 设置InnoDB为默认引擎：在配置文件my.cnf中的 [mysqld] 下面加入default-storage-engine=INNODB 一句，保存。

3. 重启mysql服务器：mysqladmin -u root -p shutdown或者service mysqld restart 登录mysql数据库，在mysql>提示符下搞入show engines;命令。如果出现 InnoDB |DEFAULT，则表示我们 设置InnoDB为默认引擎成功。

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