Question

大家好，我可以重写查询：

select userid from User where userid not in(select userid from UserRole where roleid in(8));

作为加入？

问题是一个用户可能有多个角色先感谢您。

mysql> desc User;  
+--------------------+-------------------+------+-----+---------+----------------+  
| Field              | Type              | Null | Key | Default | Extra          |  
+--------------------+-------------------+------+-----+---------+----------------+  
| userId             | int(11)           | NO   | PRI | NULL    | auto_increment |  
| userName           | varchar(50)       | YES  |     | NULL    |                |

...和其他用户相关的列

mysql> desc UserRole;  
+--------+---------+------+-----+---------+-------+  
| Field  | Type    | Null | Key | Default | Extra |  
+--------+---------+------+-----+---------+-------+  
| userId | int(11) | NO   | PRI | 0       |       |  
| roleId | int(11) | NO   | PRI | 0       |       |  
+--------+---------+------+-----+---------+-------+

Answer 1

我没有对此进行测试，但我认为它有效。

select userID from user 
left join UserRole 
on user.userID = UserRole.userID 
and UserRole.roleID = 8
where UserRole.roleID IS NULL

Answer 2

也许这会有用吗？

select userid from User 
left outer join
(select userid, roleid from UserRole where roleid in(8)) v
on User.userid = v.userid
where roleid is null;

Answer 3

我认为这应该可以让你拥有8个以外角色的每个人

select userid from User
where not exists 
  (select UserId from UserRole
     where UserRole.userid = User.userid and roleid not in(8) )

Answer 4

如果您想要提高可读性，可以使用EXCEPT子句。

即

select userId from user 
except
select userId from UserRole where roleId <> 8

不确定MySQL是否支持“除外”。

重写Subquery（不在）中作为Join

4 个答案: