php - MySQL查询: How to join multiple table with statment

Question

我有下面的mysql查询。但它不起作用。

SELECT  CASE
        WHEN isLevel = '1' THEN 'Mahasiswa'
        WHEN isLevel = '2' THEN 'Dosen'
        WHEN isLevel = '3' THEN 'Karyawan'
        ELSE 'Admin'
        END as level 
FROM mhs LEFT JOIN if(isLevel=1,'mahasiswa','dosen') ON username=iduser 
WHERE blabala.

如果“isLevel=1”我想将mhs与mahasiswa表连接，如果“isLevel=2”将mhs与dosen表连接，...我应该如何编写查询？

请帮助我。 谢谢。

Answer 1

您无法有条件地加入。但使用 2 个左连接来获取两个表

Select  CASE
    WHEN isLevel = '1' THEN 'Mahasiswa'
    WHEN isLevel = '2' THEN 'Dosen'
    WHEN isLevel = '3' THEN 'Karyawan'
ELSE 'Admin'
END as level 
from mhs 
left join mahasiswa m on m.username=iduser
left join dosen d on d.username=iduser