我写了一句SQL如下:
create table if not exists Teachings(
teacher varchar(255),
classid varchar(32) references Class(id)
check(teacher in (select username from Users where role = 'teacher'))
);
但是在执行的时候报错(MySQL版本5.6.30):
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'check(teacher in (select username from Users where role = 'teacher')))' at line 4
是不是MySQL中的check约束不能包含子查询呢?如果是,我的这句SQL应该怎么实现呢?
PS:完整的SQL见这里
DDL漏了个逗号
MySQL并不支持CHECK约束,参见MySQL文档
可以用触发器来实现