如何防止存儲過程中的除零錯誤？

Question

我試圖從服務器資源管理器執行my brand-spanking-new Stored Procedure，我得到：

消息8134，級別16，狀態1，過程duckbilledPlatypi，13號線 除以零遇到的錯誤。

這裏是（13）牽連的行：

@Week1End Week1End, 

...和在多個上下文：

DECLARE 
@Week1End datetime, 
@Week2begin datetime 

Select Ind.Description, 
    @BegDate BegDate, 
    @Week1End Week1End, 
    @Week1End Week2Begin, 
    @EndDate EndDate, 

對於充分披露/上下文中，這裏是在整個SP，因爲它現在存在：

CREATE PROCEDURE [dbo].[duckbilledPlatypi] 
    @Unit varchar(25), 
    @BegDate datetime, 
    @EndDate datetime 
AS 

DECLARE 
@Week1End datetime, 
@Week2begin datetime 

Select Ind.Description, 
    @BegDate BegDate, 
    @Week1End Week1End, 
    @Week1End Week2Begin, 
    @EndDate EndDate, 
    SUM(CASE WHEN Ind.InvoiceDate BETWEEN @BegDate AND @Week1End THEN Ind.QtyShipped ELSE 0 END) 
Week1Usage, 
    SUM(CASE WHEN Ind.InvoiceDate BETWEEN @Week2Begin AND @EndDate THEN Ind.QtyShipped ELSE 0 END) 
Week2Usage, 
    SUM(CASE WHEN Ind.InvoiceDate BETWEEN @BegDate AND @Week1End THEN Ind.Price ELSE 0 END) 
Week1Price, 
    SUM(CASE WHEN Ind.InvoiceDate BETWEEN @Week2Begin AND @EndDate THEN Ind.Price ELSE 0 END) - 
    SUM(CASE WHEN Ind.InvoiceDate BETWEEN @BegDate AND @Week1End THEN Ind.QtyShipped ELSE 0 END) 
UsageVariance, 
    SUM(CASE WHEN Ind.InvoiceDate BETWEEN @Week2Begin AND @EndDate THEN Ind.QtyShipped ELSE 0 END) - 
    SUM(CASE WHEN Ind.InvoiceDate BETWEEN @BegDate AND @Week1End THEN Ind.Price ELSE 0 END) 
PriceVariance, 
    (SUM(CASE WHEN Ind.InvoiceDate BETWEEN @Week2Begin AND @EndDate THEN Ind.QtyShipped ELSE 0 
END) - 
    SUM(CASE WHEN Ind.InvoiceDate BETWEEN @BegDate AND @Week1End THEN Ind.Price ELSE 0 END)) 
    /SUM(CASE WHEN Ind.InvoiceDate BETWEEN @BegDate AND @Week1End THEN Ind.Price ELSE 0 END) 
PercentageOfPriceVariance 
    From InvoiceDetail Ind 
    Where Ind.Unit = @Unit 
    AND Ind.InvoiceDate BETWEEN @BegDate AND @EndDate 
    Group By Ind.Description 

我的猜測是@ Week1End Week1End失敗，因爲它不是給定一個值，因此是空的。我不知道我是否應該做這樣的事情，以防止0 /空：

DECLARE 
@Week1End datetime = BegDate + 6; 
@Week2begin datetime = BegDate + 7; 

...或者是這樣的：

Select Ind.Description, 
    @BegDate BegDate, 
    @Week1End BegDate+6, 
    @Week2Begin BegDate+7, 
    @EndDate EndDate, 

...或別的東西完全。

正如你可能會說，我不知道日期數學應該如何實際完成。什麼日期，真正需要的是有：

Week1Begin is the "BegDate" the user provided as a parameter 
Week1End needs to be six days after Week1Begin 
Week2Begin needs to be seven days after Week1Begin 
Week2End is the "EndDate" the user provided as a parameter 

例如，如果用戶輸入「2015年12月27日」爲BegDate和「2016年1月6日」爲結束日期，這些值必須是：

Week1Begin = 12/27/2015 
Week1End = 1/2/2016 
Week2Begin = 1/3/2016 
Week2End = 1/6/2016 (week2 is only a four-day week in this case, due to what the user entered) 

我該怎麼做才能確保在這裏沒有發生零點的div？

Answer 1

你可以使用NULLIF：

(SUM(CASE WHEN Ind.InvoiceDate BETWEEN @Week2Begin AND @EndDate THEN Ind.QtyShipped ELSE 0 
END) - 
    SUM(CASE WHEN Ind.InvoiceDate BETWEEN @BegDate AND @Week1End THEN Ind.Price ELSE 0 END)) 
    /NULLIF(SUM(CASE WHEN Ind.InvoiceDate BETWEEN @BegDate AND @Week1End THEN Ind.Price ELSE 0 END),0) 
PercentageOfPriceVariance 

所以當除數是0的enitre結果將是NULL。如果你需要的話特殊值增加COALESCE：

COALESCE(exp1/NULLIF(exp2, 0), special_value) AS result 

LiveDemo