mysql离开了join和sum group by

Question

您好我使用此mysql代码生成以下数据：

代码：

SELECT L.LEAVETYPE, LA.IDLEAVETYPE, LA.IDLEAVETABLE, SUM( LA.NOOFDAYS ) 
FROM LEAVETYPE AS L
LEFT JOIN LEAVEAPPLICATION AS LA ON LA.IDLEAVETYPE = L.IDLEAVETYPETABLE
GROUP BY L.LEAVETYPE

当我添加Where条件时，它只会显示带有值的LeaveType。如何显示所有的leavetype，包括null（如第一张图片中所示）？

SELECT L.LEAVETYPE, LA.IDLEAVETYPE, LA.IDLEAVETABLE, SUM(LA.NOOFDAYS)
FROM LEAVETYPE AS L
LEFT JOIN LEAVEAPPLICATION AS LA ON LA.IDLEAVETYPE = L.IDLEAVETYPETABLE
WHERE LA.IDSTAFFTABLE='24'
GROUP BY L.LEAVETYPE

Answer 1

将idstafftable条件移动到连接而不是where：

LEFT JOIN LEAVEAPPLICATION AS LA ON LA.IDLEAVETYPE = L.IDLEAVETYPETABLE AND LA.IDSTAFFTABLE='24'