sql - mysql 左连接和求和分组依据

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。我怎样才能显示所有的离开类型，包括空(如第一张图片所示)？

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 条件移至连接而不是 where:

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