mysql 默认的数据库引擎是MyISAM，不支持事务和外键，也可使用支持事务和外键的InnoDB。

查看当前数据库的所支持的数据库引擎以及默认数据库引擎：

我服务器环境系统为：centos5.3  mysql版本为：5.0.45

 mysql> show engines;
+————+———-+——————————————————-                                          ———+
| 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 tab                                          les      |
| InnoDB     | DISABLED | Supports transactions, row-level locking, and foreign                                           keys     |
| BerkeleyDB | DISABLED | Supports transactions and page-level locking                                                             |
| BLACKHOLE  | NO       | /dev/null storage engine (anything you write to it dis                                          appears) |
| 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                                                                                  |
+————+———-+——————————————————-                                          ———+
12 rows in set (0.00 sec)

mysql>

通过上面我们可以发现，默认的数据库引擎是MyISAM ，在support中，显示为YES的为支持，NO为不支持，DEFAULT为默认，DISABLED为关闭，InooDB可以在my.cnf中配置开启：

注释掉my.cnf配置文件中“skip-innodb ”部分，保存重启服务。

再次查看，DISABLED就显示为YES了。

然后在my.cnf中[mysqld] 部分添加代码：

default-storage-engine=InnoDB

重启mysqld，再次show engines 确认。

数据库引擎默认就更改为InnoDB。

在windows环境中，数据库默认引擎为InnoDB，也可以通过修改my.ini 来定义默认引擎。方法一样。

PS：

在linux中的my.cnf配置文件中有这么一段：

# Uncomment the following if you are using InnoDB tables
#innodb_data_home_dir = /var/lib/mysql/
#innodb_data_file_path = ibdata1:10M:autoextend
#innodb_log_group_home_dir = /var/lib/mysql/
#innodb_log_arch_dir = /var/lib/mysql/
# You can set .._buffer_pool_size up to 50 – 80 %
# of RAM but beware of setting memory usage too high
#innodb_buffer_pool_size = 16M
#innodb_additional_mem_pool_size = 2M
# Set .._log_file_size to 25 % of buffer pool size
#innodb_log_file_size = 5M
#innodb_log_buffer_size = 8M
#innodb_flush_log_at_trx_commit = 1
#innodb_lock_wait_timeout = 50

使用InnoDB引擎的建议取消注释，以优化数据库性能。