SQL-总和然后除以零问题

Question

我试图对2列求和并将它们除以另一列，但是在除以零时遇到了问题。

数学本质上是Sum（a）/ Sum（b）

我的代码：

SELECT
      SUM(Inventory.QuantityOutstanding) as Quantity,   

      SUM(inventory.TotalValueOutstanding) as ExtValue,

      (SELECT NULLIF(sum(Inventory.TotalValueOutstanding), 0) /
      NULLIF(SUM(Inventory.QuantityOutstanding), 0)  FROM Inventory)  as AcctValue

FROM Inventory 
GROUP BY inventory.TotalValueOutstanding 

我的预期结果：

| Quantity | Extvalue  | AcctValue
|  -10.00  | -92.00    |  0.11
|   13.00  | 0.00      |  0
|   0.00   | 0.00      |  0
|   2.00   | 16.00     |  0.125

我的实际输出：

| Quantity | Extvalue  | AcctValue
|  -10.00  | -92.00    |  76.603066544004906470
|   13.00  | 0.00      |  76.603066544004906470
|   0.00   | 0.00      |  76.603066544004906470
|   2.00   | 16.00     |  76.603066544004906470

Answer 1

我不确定如何将它们分组，但是我认为这是某种项目或ID？ 为了争辩，我已经调用了ColumnID，但是您可以将其替换为实际使用的内容（例如InventoryItemName？）。

然后，您可以尝试执行此操作，它仅检查未清数量是否为0。如果为0，则答案仅为0，否则按常规计算公式。

SELECT
   Inventory.ColumnID,
   SUM(Inventory.QuantityOutstanding) as Quantity,   

   SUM(inventory.TotalValueOutstanding) as ExtValue,

   IIF(SUM(Inventory.QuantityOutstanding) = 0
        ,0
        ,isnull(sum(Inventory.TotalValueOutstanding), 0) /
           sum(Inventory.QuantityOutstanding)
       ) as AcctValue
FROM 
   Inventory 
GROUP BY
   Inventory.ColumnID

Answer 2

问题是您的子查询：

SELECT SUM(i.QuantityOutstanding) as Quantity,   
       SUM(i.TotalValueOutstanding) as ExtValue,
       (NULLIF(SUM(i.TotalValueOutstanding), 0) /
               NULLIF(SUM(i.QuantityOutstanding), 0)
       ) as AcctValue
FROM Inventory i
GROUP BY i.TotalValueOutstanding ;

我发现双NULLIF()有点令人困惑。 使用CASE可能更清楚：

SELECT SUM(i.QuantityOutstanding) as Quantity,   
       SUM(i.TotalValueOutstanding) as ExtValue,
       (CASE WHEN SUM(i.QuantityOutstanding) = 0 THEN 0
             ELSE SUM(i.TotalValueOutstanding) /                   
                  SUM(i.QuantityOutstanding)
        END) as AcctValue
FROM Inventory i
GROUP BY i.TotalValueOutstanding ;