3
由于(Department_Code,Course_Code)行,以下查询给出错误“#1241 - 操作数应包含1列”。当我用(Course_Code)代替它时,它可以工作。然而,这不是我想要的GROUP BY CASE的问题
SELECT * FROM Classes
GROUP BY CASE
WHEN (1) THEN
Department_Code
ELSE CASE WHEN (2) THEN
(Department_Code, Course_Code)
ELSE Class_ID
END
END
我怎么能按Department_Code,当条件(2)满意是Course_Code?