mysql - 如何在 MYSQL 中获取主管的姓名而不是 UserID + INNER JOIN

Question

这是我的桌子：

从用户中选择 *

USERID  NAME    STATUS
1       AAA     Member
2       BBB     Member
3       CCC     Supervisor
4       DDD     Member
5       EEE     Member

从出席中选择 *

NO  DATE        SUPERVISOR  MEMBER
1   2019-12-11  3           1
2   2019-12-11  3           2
3   2019-12-11  3           4
4   2019-12-11  3           5

从详细信息中选择 *

NO  USERID  ATTENDANCE  REASON
1   1       0           SICK
2   2       1           -
3   4       1           -
4   5       1           -

我想要的结果：

USERID  DATE        NAME    REASON  SUPERVISOR
1       2019-12-11  AAA     SICK    CCC
2       2019-12-11  BBB     -       CCC
3       2019-12-11  DDD     -       CCC
4       2019-12-11  EEE     -       CCC

我尝试过的 SQL 调用主管的用户 ID，而不是主管的姓名。

SELECT d.userid, a.date, u.name, d.reason, a.supervisor FROM attendance a INNER JOIN detail d on a.userid = d.userid INNER JOIN user u on d.userid = u.userid WHERE d.attendance=0

我需要有关 sql 的帮助来调用主管的姓名而不是用户 ID。谢谢..

Answer 1

您必须加入用户表两次，因为您要匹配成员名称和主管名称。我也使用过LEFT JOIN，因为有时原因没有价值，但您仍想从其他表中提取记录。

SELECT u1.userid, a.date, u1.name, d.reason, u2.name AS supervisor
FROM user u1
LEFT JOIN attendance a ON u1.userid = a.member
LEFT JOIN detail d ON u1.userid = d.userid
LEFT JOIN user u2 ON a.supervisor = u2.userid
WHERE d.attendance = 0

Answer 2

SELECT u1.userid, a.date, u1.name As Name, d.reason, u2.name AS supervisor
FROM user u1
LEFT JOIN attendance a ON u1.userid = a.member
LEFT JOIN detail d ON u1.userid = d.userid
LEFT JOIN user u2 ON a.supervisor = u2.userid
WHERE d.attendance=0;