Question

样本表数据

Declare @t table (PolicyNumber varchar(10),Val decimal(18,2),Fund varchar(5),Tenure varchar(10))
INSERT INTO @t(PolicyNumber,Val,Fund,Tenure)VALUES 
('ASWPP',10.2,'T001','Secure'),
('ASWPP',5.0,'T002','Secure'),
('ASWPP',5.0,'T003','Secure'),
('XPPW',15.2,'T001','Growth'),
('XPPW',10.2,'T002','Growth'),
('XPPW',10.2,'T003','Growth'),
('XXXX',20.2,'T001','Secure'),
('XXXX',10.2,'T002','Secure'),
('XXXX',10.2,'T003','Secure')

如何根据策略编号从同一表中进行减法。

我需要从中减去Fund = 002 其他基金（T001，T003）

我需要获得如下输出：

 PolicyNumber   Val        Fund           Tenure
 ASWPP          5.2        T001            Secure     
 ASWPP          0.0        T003            Secure     
 XPPW           5.2        T001            Growth     
 XPPW           0.2        T003            Growth     
 XXXX           10.2       T001           Secure     
 XXXX           0.0        T003            Secure

建议我最好的方式

Answer 1

您需要将表连接到自身，其中一个实例排除T002个记录，一个实例仅包含它们：

SELECT  t.PolicyNumber,
        Val = t.Val - ISNULL(t2.Val, 0),
        t.Fund,
        t.Tenure
FROM    @T AS t
        LEFT JOIN @T AS t2
            ON t2.PolicyNumber = t.PolicyNumber
            AND t2.Fund = 'T002'
WHERE   t.Fund <> 'T002';

如果PolicyNumber和Fund的类型不是唯一的，那么您可能需要一个子查询来避免重复：

SELECT  t.PolicyNumber,
        Val = t.Val - ISNULL(t2.Val, 0),
        t.Fund,
        t.Tenure
FROM    @T AS t
        LEFT JOIN 
        (   SELECT  PolicyNumber, Val = SUM(Val)
            FROM    @T 
            WHERE   Fund = 'T002'
            GROUP BY PolicyNumber
        ) AS t2
            ON t2.PolicyNumber = t.PolicyNumber
WHERE   T.Fund <> 'T002';

Answer 2

像这样加入那张桌子：

SELECT t1.PolicyNumber, t2.val - t1.val AS val, t2.Fund, t2.Tenure
  FROM t t1
  JOIN t t2
    ON t1.PolicyNumber = t2.PolicyNumber AND t2.FUND != 'T002'
 WHERE t1.FUND = 'T002';

Answer 3

这是其中一种方式。

Select a.PolicyNumber,
a.Val - t2.Val as NewVal,
a.Fund, a.Tenure
from @t a
join
(
    Select * from @t
    Where Fund = 'T002'
) t2
ON a.PolicyNumber = t2.PolicyNumber
Where a.Fund <> 'T002'

如何根据ID从同一个表中进行减法

3 个答案: