如何计算SQL中两个SELECT(Access、JetSQL)的差异

Question

我需要从同一个表联接中获得两个SUM...WHERE查询的差异：

SELECT SUM(Service_template.Service_fee)
FROM (Service_template LEFT JOIN Service ON Service_template.Service_Code = Service.Service_Code) LEFT JOIN Bill ON Service.Service_ID = Bill.Service_ID
WHERE Bill.Service_ID IS NOT NULL

和

SELECT SUM(Service_template.Service_fee)
FROM (Service_template LEFT JOIN Service ON Service_template.Service_Code = Service.Service_Code) LEFT JOIN Bill ON Service.Service_ID = Bill.Service_ID

我尝试过使用UNION，但它返回两行，而不是我可以计算的两列。

我该怎么做？我觉得我错过了一些琐碎的事情，所以提前谢谢！

Answer 1

如果您想要这三个值，您可以使用条件聚合：

SELECT SUM(IIF(b.Service_ID IS NOT NULL, st.Service_fee, 0)) as total_1,
SUM(b.Service_Id) as total_2,
SUM(IIF(b.Service_ID IS NULL, st.Service_fee, 0)) as diff      
FROM (Service_template as st LEFT JOIN
Service as s
ON st.Service_Code = s.Service_Code
) LEFT JOIN
Bill as b
ON s.Service_ID = b.Service_ID;

如果你只想要SUM()，其中Service_Id是NULL，那么：

SELECT SUM(b.Service_Id) as diff      
FROM (Service_template as st LEFT JOIN
Service as s
ON st.Service_Code = s.Service_Code
) LEFT JOIN
Bill as b
ON s.Service_ID = b.Service_ID
WHERE b.Service_ID IS NULL;

Answer 2

这应该有效：

Select
Sum(T1.Sum1),
Sum(T2.Sum2),
Sum(T1.Sum1) - Sum(T2.Sum2) As Diff1,
Sum(T2.Sum2) - Sum(T1.Sum1) As Diff2
From
(SELECT SUM(Service_template.Service_fee) As Sum1 FROM (Service_template LEFT JOIN Service ON Service_template.Service_Code = Service.Service_Code) LEFT JOIN Bill ON Service.Service_ID = Bill.Service_ID WHERE Bill.Service_ID IS NOT NULL) As T1,
(SELECT SUM(Service_template.Service_fee) As Sum2 FROM (Service_template LEFT JOIN Service ON Service_template.Service_Code = Service.Service_Code) LEFT JOIN Bill ON Service.Service_ID = Bill.Service_ID) As T2