SQL - DateAdd 内的 If 语句答案

【问题标题】：SQL - If Statement Inside DateAddSQL - DateAdd 内的 If 语句
【发布时间】：2017-07-11 14:51:10
【问题描述】：

我对 SQL 非常陌生，但我真的很喜欢它，并希望能做得更好。

在我的代码中，我将 3 个表合并在一起，然后为该合并创建几列。我创建了一个“DaysOfStock”列，并希望将每列中的数字添加到当前日期。问题是“DaysOfStock”是一个“if”函数，我不知道如何将它添加到“DayAdd”函数中。我遇到问题的代码部分如下。

SELECT Cust.Article,
    IsNull(stock.StockQuantity,0) StockQuantity,
    IsNull(orders.OpenQty,0) OpenOrders,
    IsNull(usage.[3MonUsage], 0) [3MonUsage], IsNull(usage.EAU, 0) [EAU],
    ROUND(IsNull(usage.EAU, 0)/366,0) DailyUsage,
    CASE WHEN IsNull(usage.EAU, 0)/366 = 0 THEN ROUND(IsNull(stock.StockQuantity,0)/(IsNull(orders.OpenQty, 0)/366),2)
    ELSE ROUND(IsNull(stock.StockQuantity,0)/(IsNull(usage.EAU, 0)/366),2) END AS DaysOfStock
    DateAdd(day, **DaysOfStock**, GetDate())
FROM TeslaArts 
        LEFT OUTER JOIN usage ON CustArts.Article = usage.Article
        LEFT OUTER JOIN stock ON CustArts.Article = stock.Article
        LEFT OUTER JOIN orders ON CustArts.Article = orders.Article
WHERE (orders.OpenQty > 0 AND usage.[3MonUsage] > 0)
    OR (orders.OpenQty = 0 AND usage.[3MonUsage] > 0)
    OR (orders.OpenQty > 0 AND usage.[3MonUsage] = 0)

如果有什么不清楚的地方请告诉我。提前感谢您的帮助。 -亚历克斯

【问题讨论】：

标签： sql if-statement calculated-columns case-when dateadd

【解决方案1】：

嗯，很简单，只需重复相同的代码：

SELECT Cust.Article,
    IsNull(stock.StockQuantity,0) StockQuantity,
    IsNull(orders.OpenQty,0) OpenOrders,
    IsNull(usage.[3MonUsage], 0) [3MonUsage], IsNull(usage.EAU, 0) [EAU],
    ROUND(IsNull(usage.EAU, 0)/366,0) DailyUsage,
    CASE WHEN IsNull(usage.EAU, 0)/366 = 0 THEN ROUND(IsNull(stock.StockQuantity,0)/(IsNull(orders.OpenQty, 0)/366),2)
    ELSE ROUND(IsNull(stock.StockQuantity,0)/(IsNull(usage.EAU, 0)/366),2) END AS DaysOfStock,
    DateAdd(day,
           CASE WHEN IsNull(usage.EAU, 0)/366 = 0 THEN
               ROUND(IsNull(stock.StockQuantity,0)/(IsNull(orders.OpenQty, 0)/366),2)
          ELSE
              ROUND(IsNull(stock.StockQuantity,0)/(IsNull(usage.EAU, 0)/366),2)
          END,
          GetDate()) AS ProjectedDate
FROM TeslaArts 
        LEFT OUTER JOIN usage ON CustArts.Article = usage.Article
        LEFT OUTER JOIN stock ON CustArts.Article = stock.Article
        LEFT OUTER JOIN orders ON CustArts.Article = orders.Article
WHERE (orders.OpenQty > 0 AND usage.[3MonUsage] > 0)
    OR (orders.OpenQty = 0 AND usage.[3MonUsage] > 0)
    OR (orders.OpenQty > 0 AND usage.[3MonUsage] = 0)

【讨论】：