Mysql 为什么可以';我不能这样添加外键约束吗?
表:Mysql 为什么可以';我不能这样添加外键约束吗?,mysql,sql,database,foreign-keys,Mysql,Sql,Database,Foreign Keys,表: CREATE TABLE `relation` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(40) NOT NULL, `gender` tinyint(1) DEFAULT NULL, PRIMARY KEY (`id`), UNIQUE KEY `unique_relation` (`name`) ) ENGINE=InnoDB DEFA
CREATE TABLE `relation` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(40) NOT NULL,
`gender` tinyint(1) DEFAULT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `unique_relation` (`name`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8
CREATE TABLE `invite` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`date_sent` date NOT NULL,
`user_id` int(10) unsigned NOT NULL,
`relation_id` int(10) unsigned NOT NULL,
`email` varchar(255) NOT NULL,
`code` varchar(255) NOT NULL,
PRIMARY KEY (`id`),
KEY `fk_user` (`user_id`),
CONSTRAINT `fk_user` FOREIGN KEY (`user_id`) REFERENCES `user` (`id`) ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=utf8
执行的SQL语句为:
ALTER TABLE `invite`
ADD CONSTRAINT `fk_relation`
FOREIGN KEY (`relation_id`)
REFERENCES `relation` (`id`)
ON DELETE CASCADE ON UPDATE RESTRICT
Mysql错误:
SQLSTATE[HY000]:一般错误:1005无法创建表“dbtest.#sql-d00_39”(错误号:121)。
relation.id和invite.relation\u id列的类型相同,int(10)为无符号
更新
添加此键时,表invite为空。
表关系有3行。请尝试以下操作:
ALTER TABLE invite
ADD CONSTRAINT fk_relation
FOREIGN KEY (relation_id)
REFERENCES relation(id)
根据doc语法是否正确现在,用于创建外键的DDL自动包含用于指定“删除”和“更新”操作的语句。但是,对于“Delete”,它包含“ON Delete RESTRICT”语句,该语句似乎不是有效的T-SQL语句 试试这个: 通过选中添加约束fk_关系更改表invite 外键(关系\ id)引用关系(id)
实际上,invite表是空的吗? ALTER TABLE invite WITH CHECK ADD CONSTRAINT fk_relation FOREIGN KEY (relation_id) REFERENCES relation (id)