SQL中的计算和防止除以零

Question

我正在尝试修改基于游标的查询。

查询会根据多个值计算某些统计信息。在第一、二、三CASE下面的sn-p中算出Unit1的幸福。这些字段中的任何一个都是 0（它们永远不能是 NULL）我会得到一个 Divide by Zero 错误。我可以在每个字段 (Unit2 + 1) / (Unit1 + 1) 中添加 1，这将停止错误。但是，这似乎是一个障碍，它可能会给出不正确的结果。 IE。 Unit1 需要相同数量的 Unit2 才能让他们开心。如果我有一个Unit1 而没有Unit2，这个bodge 会给那张支票100% 高兴。所以我的第一个问题是如何防止除以零但不扭曲结果。每个CASE给我一个%快乐

Select 

CASE WHEN ((Unit2 / Unit1) * 100) > 100 Then 100 Else ((Unit2 / Unit1) * 100) END Unit1Happy1,
CASE WHEN ((Stock3 / (Unit1 * 2)) * 100) > 100 Then 100 Else ((Stock3 / (Unit1 * 2)) * 100) END Unit1Happy2,
CASE WHEN (((Drug3 + (Drug1 / 2)) / Unit1) * 100)  > 100 Then 100 Else (((Drug3 + (Drug1 / 2)) / Unit1) * 100)  END Unit1Happy3,
CASE WHEN (((Weapon6 + Weapon7 + Weapon8 + Weapon9) / Unit2) * 100) > 100 Then 100 ELSE (((Weapon6 + Weapon7 + Weapon8 + Weapon9) / Unit2) * 100) END Unit2Happ1,
CASE WHEN (((Stock2 + (Stock1 / 2)) / Unit2) * 100)  > 100 Then 100 Else (((Stock2 + (Stock1 / 2)) / Unit2) * 100) END Unit2Happ2

FROM tblUserFiles

我的下一个问题是我需要为每个 UnitHappiness 取最低值并将该值存储在表中。所以在tblUserFiles中有5个字段Unit1Happ，Unit2Happ ....Unit5Happ。查看上面的查询，如果Unit1Happy1 是我将该数字存储到Unit1Happ 中的最低数字，如果Unit2Happy 是我存储的最低数字，等等。

我的记录标识符是UserId，我需要为给定的UserId 或整个表运行它。

我基本上要问的是：

• 确定每个单位最低值的最佳方法是什么 计算？
• 防止被零除的最佳方法是什么 错误？
• 我能否以更好的方式解决这个问题？

更新

我正在研究以下答案中发布的建议。由于这只是一个训练练习，可能需要一段时间。我确实有一个有效的查询，它给出了我正在寻找的结果我只是不确定建议的答案是否更有效。

Update tblUserFiles Set Unit1Happ = happyvals.Unit1Happiness, Unit2Happ = happyvals.Unit2Happiness, Unit3Happ = happyvals.Unit3Happiness, Unit4Happ = happyvals.Unit4Happiness, Unit5Happ = happyvals.Unit5Happiness FROM

(SELECT ch.UserId,
Case When ch.Unit1Happy1 < ch.Unit1Happy2 And ch.Unit1Happy1 < ch.Unit1Happy3 Then ch.Unit1Happy1
            When ch.Unit1Happy2 < ch.Unit1Happy1 And ch.Unit1Happy2 < ch.Unit1Happy3 Then ch.Unit1Happy2 
            Else ch.Unit1Happy3
End As Unit1Happiness,
CASE WHEN ch.Unit2Happy1 > ch.Unit2Happy2 THEN ch.Unit2Happy1
            ELSE ch.Unit2Happy2
END AS Unit2Happiness, 
ch.Unit3Happy1 AS Unit3Happiness,
ch.Unit4Happy1 AS Unit4Happiness,
ch.Unit5Happy1 AS Unit5Happiness
FROM
(

Select 
UserId,
CASE    WHEN Unit2 = 0 OR Unit1 = 0 THEN 0 
        WHEN ((Unit2 / Unit1) * 100) > 100 Then 100 
        ELSE ((Unit2 / Unit1) * 100) 
END Unit1Happy1,
CASE    WHEN Stock3 = 0 OR Unit1 = 0 THEN 0 
        WHEN ((Stock3 / (Unit1 * 2)) * 100) > 100 THEN 100 
        ELSE ((Stock3 / (Unit1 * 2)) * 100) 
END Unit1Happy2,
CASE    WHEN Unit1 = 0 THEN 0 
        WHEN Drug3 = 0 AND Drug1 = 0 THEN 0
        WHEN Drug1 = 0 THEN 
                        CASE WHEN (Drug3 / Unit1) * 100 > 100 THEN 100
                            ELSE (Drug3 / Unit1) * 100
                        END
        WHEN Drug3 = 0 THEN
                        CASE WHEN (Drug1 / 2) / Unit1 > 100 THEN 100
                            ELSE (Drug1 / 2) / Unit1
                        END
        ELSE 
            CASE WHEN (((Drug3 + (Drug1 / 2)) / Unit1) * 100) > 100 THEN 100
                ELSE (((Drug3 + (Drug1 / 2)) / Unit1) * 100)
            END

END Unit1Happy3,
CASE    WHEN Unit2 = 0 THEN 0 
        WHEN (Weapon6 + Weapon7 + Weapon8 + Weapon9) = 0 THEN 0
        WHEN (((Weapon6 + Weapon7 + Weapon8 + Weapon9) / Unit2) * 100) > 100 THEN 100
        ELSE (((Weapon6 + Weapon7 + Weapon8 + Weapon9) / Unit2) * 100)
END Unit2Happy1,
CASE    WHEN Unit2 = 0 THEN 0
        WHEN Stock1 = 0 AND Stock2 = 0 THEN 0
        WHEN Stock1 = 0 THEN
            CASE WHEN ((Stock2 / Unit2) * 100)  > 100 THEN 100
                ELSE ((Stock2 / Unit2) * 100)
            END
        WHEN Stock2 = 0 THEN
            CASE WHEN (((Stock1 / 2) / Unit2) * 100)  > 100 THEN 100
                ELSE (((Stock1 / 2) / Unit2) * 100)
            END
        WHEN (((Stock2 + (Stock1 / 2)) / Unit2) * 100)  > 100 THEN 100
        ELSE (((Stock2 + (Stock1 / 2)) / Unit2) * 100)
END Unit2Happy2,    
CASE    WHEN Unit2 = 0 OR Unit3 = 0 THEN 0 
        WHEN ((Unit2 / Unit3) * 100) > 100 THEN 100 
        ELSE ((Unit2 / Unit3) * 100) 
END Unit3Happy1,
CASE    WHEN Unit2 = 0 OR Unit4 = 0 THEN 0 
        WHEN ((Unit2 / Unit4) * 100) > 100 THEN 100 
        ELSE ((Unit2 / Unit4) * 100) 
END Unit4Happy1,
CASE    WHEN Unit2 = 0 OR Unit5 = 0 THEN 0 
        WHEN ((Unit2 / Unit5) * 100) > 100 THEN 100 
        ELSE ((Unit2 / Unit5) * 100) 
END Unit5Happy1
FROM tblUserFiles) ch) happyvals
Join tblUserFiles ON tblUserFiles.UserID = happyvals.UserID

Answer 1

在每个分组周围放置一个nullif(Unit1, 0) 吗？

Answer 2

类似的东西。

这个想法是将您的除法包装在 UDF（标量用户定义函数）中......并使用“Max(v)”技巧。

下面的代码可能并不完美，我提供了这个想法。

99.9% 的情况下，光标的表现都很糟糕。尝试在没有游标的情况下解决这个问题。

/* or Create */
ALTER FUNCTION dbo.udfSafeDivision (@num float , @denom float)

RETURNS float

AS

BEGIN
    declare @returnValue float
    select @returnValue = 0

        if(isnull(@denom,0) != 0)
        BEGIN
            select @returnValue = convert(float, convert(float, @num)/convert(float, @denom))
        END
    return @returnValue


END


GO


IF OBJECT_ID('tempdb..#TableOne') IS NOT NULL
begin
        drop table #TableOne
end


CREATE TABLE #TableOne
( 
SurrogateKey int IDENTITY(1001, 1), 
Unit1 int , 
Unit2 int , 
Stock1 int , 
Stock2 int , 
Stock3 int ,

Drug1 int , 
Drug3 int , 
Weapon6  int ,  Weapon7  int ,  Weapon8  int ,  Weapon9 int

)

Insert into #TableOne (Unit1, Unit2, Stock1, Stock2 , Stock3 , Drug1, Drug3 , Weapon6 , Weapon7 , Weapon8 , Weapon9)
select 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0
UNION ALL select 1 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0
UNION ALL select 1 , 2 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0
UNION ALL select 1 , 2 , 3 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0
UNION ALL select 1 , 2 , 3 , 4 , 0 , 0 , 0 , 0 , 0 , 0 , 0
UNION ALL select 1 , 2 , 3 , 4 , 5 , 0 , 0 , 0 , 0 , 0 , 0
UNION ALL select 1 , 2 , 3 , 4 , 5 , 6 , 0 , 0 , 0 , 0 , 0
UNION ALL select 1 , 2 , 3 , 4 , 5 , 6 , 7 , 0 , 0 , 0 , 0
UNION ALL select 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 0 , 0 , 0
UNION ALL select 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 0 , 0
UNION ALL select 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 0
UNION ALL select 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11


UNION ALL select 5 , 1 ,  0 , 0 , 0 , 0 , 0 , 0 , 0 , 0 , 0
UNION ALL select 5 , 0 ,  0 , 0 , 5 , 0 , 0 , 0 , 0 , 0 , 0
UNION ALL select 10 , 0 ,  0 , 0 , 0 , 5 , 10 , 0 , 0 , 0 , 0
UNION ALL select 0 , 1 ,  0 , 0 , 0 , 5 , 10 , 10 , 20 , 30 , 40
UNION ALL select 0 , 50 ,  20 , 10 , 0 , 0 , 0 , 0 , 0 , 0 , 0


SELECT 
  (SELECT Max(v) 
   FROM (VALUES (Unit1Happy1), (Unit1Happy2), (Unit1Happy3),  (Unit2Happ1), (Unit2Happ2)) AS value(v)) as [MaxValue]
   ,    '--------' as Sep1
   , derived1.*

FROM
(
Select 

CASE WHEN ((dbo.udfSafeDivision(Unit2 , Unit1)) * 100) > 100 Then 100 Else (dbo.udfSafeDivision(Unit2 , Unit1) * 100) END Unit1Happy1,
CASE WHEN (dbo.udfSafeDivision(Stock3 , (Unit1 * 2)) * 100) > 100 Then 100 Else (dbo.udfSafeDivision(Stock3 , (Unit1 * 2)) * 100) END Unit1Happy2,
CASE WHEN (dbo.udfSafeDivision((Drug3 + (Drug1 / 2)) , Unit1) * 100)  > 100 Then 100 Else (dbo.udfSafeDivision((Drug3 + (Drug1 / 2)) , Unit1) * 100)  END Unit1Happy3,
CASE WHEN (dbo.udfSafeDivision((Weapon6 + Weapon7 + Weapon8 + Weapon9) , Unit2) * 100) > 100 Then 100 ELSE (dbo.udfSafeDivision((Weapon6 + Weapon7 + Weapon8 + Weapon9) , Unit2) * 100) END Unit2Happ1,
CASE WHEN (dbo.udfSafeDivision((Stock2 + (Stock1 / 2)) , Unit2) * 100)  > 100 Then 100 Else (dbo.udfSafeDivision((Stock2 + (Stock1 / 2)) , Unit2) * 100) END Unit2Happ2
/* the below is to debug */
, '--' as Sep1
, Unit1, Unit2, Stock1, Stock2 , Stock3 , Drug1, Drug3 , Weapon6 , Weapon7 , Weapon8 , Weapon9
, dbo.udfSafeDivision(Unit2 , Unit1) as Div1
, dbo.udfSafeDivision(Stock3 , (Unit1 * 2)) as Div3

FROM #TableOne
) as derived1



IF OBJECT_ID('tempdb..#TableOne') IS NOT NULL
begin
        drop table #TableOne
end