计算SQL中所选Ids的列总和

Question

这些是我的表:

• 成员:Id, Points
• 购物车注册:Id, Member_Id, CartId, RegisterDate, Point
• SelectetMembers:Id, Member_Id

会员可以在其中注册购物车CartRegister,并且Member.Points必须计算和插入会员所赚取的所有积分.所以我需要计算每个点的所有点SelectedMembers并更新Member表,但我不知道如何实现它.

以下脚本在我脑海中:

UPDATE [Member]
   SET [Points]=
    (
       SELECT SUM([CR].[Point]) AS [AllPoints]
       FROM  [CartRegister] AS [CR] 
       WHERE [CR].[Member_Id] = --???

    )
    WHERE [Members].[Member].[Id] IN  ( SELECT Member_Id From SelectedMembers  )

所以我很困惑Select Sum(Point)如果我使用的是where子句

        WHERE [CR].[Member_Id] IN ( Select Member_Id From SelectedMembers  )

然后所有成员的总和相同于所有成员点的总和,也许我需要一些像foreach你的建议是什么？

Answer 1

您可以使用CTE(公用表表达式)首先计算每个成员的点数,然后使用该更改来更新Members表:

-- this CTE takes all selected members, and calculates their total of points
;WITH MemberPoints AS
(
   SELECT 
       Member_ID,
       AllPoints = SUM(Point)
   FROM  
       CartRegister
   WHERE
       Member_ID IN (SELECT ID FROM SelectedMembers)
   GROUP BY 
       Member_ID
)
UPDATE dbo.Member  
SET Points = mp.AllPoints
FROM MemberPoints mp
WHERE dbo.Member.Member_ID = mp.Member_ID

Answer 2

检查一下：

UPDATE [Member]
SET [Points]=
(
   SELECT SUM([CR].[Point]) AS [AllPoints]
   FROM  [CartRegister] AS [CR] 
   WHERE [CR].[Member_Id] = [Member].[Id]

)
WHERE [Members].[Member].[Id] IN  ( SELECT Member_Id From SelectedMembers  )