一个关联查询的问题

pointer

两个表 users, user_group
users: id, username, password
user_group: id, uid, gid

user_group.uid 对应users.id

一个 users 可能有多个 gid.

现已知某个 users.id,
找出所有 与 users.id有相同 gid 的 users 的所有信息?

谢谢.

pointer

一个可以的方法:
select * from users where id = (select uid from user_group where gid = (select gid from user_group where uid = 1));

还有没有别的?

pointer

一个可以的方法:
select * from users where id = (select uid from user_group where gid = (select gid from user_group where uid = 1));

还有没有别的?

cg111

select users_group.uid, users.username, users.password from user_group inner join users on user_group.uid=users.id where gid in (select gid from user_group where uid=1);

你的方案应该修改为：
1>如果一个用户可以属于一个以上的组：
select * from users where id  in (select uid from user_group where gid in (select gid from user_group where uid = 1));
或者：
2>如果一个用户只能属于一个组：
select * from users where id in (select uid from user_group where gid = (select gid from user_group where uid = 1));

pointer

thanks!