Question

我有以下数据：

| Amount | Type | Employee |
| -----  | ---- | -------- |
| 500   |  A   |  001     |
| 200   |  B   |  001     |
| 300   |  A   |  002     |
| 200   |  A   |  002     |
| 100   |  B   |  002     |

在上面的方案中，所有Type A列都是正值，Type B是负值。

我需要计算每个员工的正数减去负数作为最终结果，这意味着A型减去B型。

因此，Employee 001的结果应为500 - 200 = 300，而Employee 002的结果为300 + 200 - 100 = 400。

我有以下不完整的查询：

SELECT 
 (SELECT SUM(Amount) FROM A WHERE Type = 'A') -  
 (SELECT SUM(Amount) FROM A WHERE Type = 'B') As Payable, Employee
FROM Payroll A
WHERE Company = @Company AND Month = @Month AND Year = @Year
GROUP BY Employee

在上面的查询中，语句SELECT SUM(Amount) FROM A WHERE Type = 'A'正在尝试获取已按公司，月和年列筛选的Payroll表的正数量。它没有用，因为A无法识别为有效对象。

那么我应该怎么做才能从过滤的Payroll表中获取数据，而不是必须再次将WHERE条件放入两个子查询中？

编辑：

感谢Kannan和Thomas提出的建议，但我仍然无法实现愿望的结果。现在，这是我使用CASE

修改后的查询

SELECT 
 SUM(CASE WHEN Type = 'B' THEN -Amount ELSE Amount END) As Payable, Employee
FROM Payroll A
WHERE Company = @Company AND Month = @Month AND Year = @Year
GROUP BY Employee

这是查询的结果：

| Payable | Employee |
| -----   | -------- |
| 500     |  001     |
| -200    |  001     |
| 500     |  002     |
| -100    |  002     |

不是将值相加，而是将正数和负数显示为不同的行。

请帮忙吗？

Answer 1

您必须使用表名，并且必须重复条件并过滤员工：

(SELECT SUM(Amount) FROM Payroll WHERE Type = 'A' AND Company = @Company AND Month = @Month AND Year = @Year AND Employee = A.Employee)

但是你也可以使用一种不需要子选择的不同方法：

SELECT 
 SUM(Amount * CASE WHEN = 'A' THEN 1 ELSE -1 END) As Payable, Employee
FROM Payroll A
WHERE Company = @Company AND Month = @Month AND Year = @Year
GROUP BY Employee

Answer 2

您可以查询如下：

Select Employee, Sum(Case when type = 'B' then -Amount else Amount End) as Sm
   From Payroll 
   WHERE Company = @Company AND Month = @Month AND Year = @Year
   GROUP BY Employee

使用子查询在表中使用负值减正

2 个答案: