Question

如何通过P.Id避免CASE和SUM中的NULL值。问题是我在DPB表中有多个DPB.ProductTypeId

SELECT  P.[Id], 
        CASE 
        WHEN DPB.ProductTypeId = 1 THEN SUM(DPB.BonusAmount)
        END AS [CasinoBonus]
FROM Player P           
JOIN PlayerBonus DPB ON P.[Id] = DPB.[PlayerId]
group by P.[Id],DPB.ProductTypeId

Answer 1

总和内的用例

 SELECT  P.[Id], 
            sum(CASE 
            WHEN DPB.ProductTypeId = 1 THEN DPB.BonusAmount
            else 0
            END) AS [CasinoBonus]
    FROM Player P           
    JOIN PlayerBonus DPB ON P.[Id] = DPB.[PlayerId]
    where P.[Id] is not null and DPB.[PlayerId] is not null
    group by P.[Id],DPB.ProductTypeId

Answer 2

case应该是sum()的参数。您的查询应如下所示：

SELECT P.[Id], 
       SUM(CASE WHEN DPB.ProductTypeId = 1 THEN DPB.BonusAmount
           END) AS [CasinoBonus]
FROM Player P JOIN
     PlayerBonus DPB
     ON P.[Id] = DPB.[PlayerId]
GROUP BY P.[Id];

请注意，您不需要DPB.ProductTypeId中的GROUP BY。

也就是说，您可能只是想要：

SELECT P.[Id], 
       SUM(DPB.BonusAmount) AS [CasinoBonus]
FROM Player P LEFT JOIN
     PlayerBonus DPB
     ON P.[Id] = DPB.[PlayerId] AND 
        DPB.ProductTypeId = 1
GROUP BY P.[Id];

将条件移至WHERE子句将完全不需要CASE。 LEFT JOIN保留所有玩家，即使那些没有该产品类型的玩家也是如此。

在CASE SQL SERVER中避免NULL值

2 个答案: