【转】[SQL]MySql myisam引擎不支持外键

CREATE TABLE `t1` (                                                                                      
          `id` char(1) NOT NULL,                                                                                 
          PRIMARY KEY  (`id`)                                                                                    
        ) ENGINE=InnoDB DEFAULT CHARSET=gb2312   

create table t2(
id char(1) not null,
foreign key(id) references t1(id)
);

table t2可以正确创建，但是外键并没有建立，使用show create table t2得到如下：

CREATE TABLE `t2` (                                                                                  
          `id` char(1) NOT NULL,                                                                             
          KEY `id` (`id`)                                                                                    
        ) ENGINE=MyISAM DEFAULT CHARSET=gb2312 

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指定table t2的引擎为innodb后可以正确创建

create table t2(
id char(1) not null,
foreign key(id) references t1(id)
)engine=innodb charset=gb2312;

使用show create table t2得到如下：

CREATE TABLE `t2` (                                                                                                                                                      
          `id` char(1) NOT NULL,                                                                                                                                                 
          KEY `id` (`id`),                                                                                                                                                       
          CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`id`) REFERENCES `t1` (`id`)                                                                                                       
        ) ENGINE=InnoDB DEFAULT CHARSET=gb2312 

摘自：http://blog.csdn.net/believefym/article/details/1891599