查詢維護產品庫存

Question

我正在嘗試創建庫存查詢以維護我的產品庫存。下圖顯示了我的表格結構和我嘗試過的。

我的查詢結果這一形象而這並不是我想要獲得：

我所試圖做的是：

（1）的具體數量我購買的產品？

（2）我賣出的特定產品的數量？

（3）我手裏有特定產品的數量（庫存）？

我在做什麼錯？

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我的查詢：

SELECT Product.ProductName, 
     Sum([Purchase Order Detail].Quantity) AS [Purchase Quantity], 
     Sum([Order Detail].Quantity) AS [Sales Quantity] 
FROM ([Purchase Order Detail] 
    RIGHT JOIN Product ON [Purchase Order Detail].ProductID = Product.ProductID) 
    LEFT JOIN [Order Detail] ON Product.ProductID = [Order Detail].ProductID 
GROUP BY Product.ProductName; 

Answer 1

你無法加入購和訂購表在一起，因爲你最終會擊中比您實際想要看到的更多匹配記錄。因此你的總和在你以前的查詢中是不正確的。

您可以使用子查詢來獲得您的結果。這樣的事情：

SELECT 
    Product.ProductID, 
    Product.ProductName, 
    (select sum(quantity) from [purchase order detail] where [purchase order detail].[ProductID] = product.productid) AS Purchased_quantity, 
    (select sum(quantity) from [order detail] where [order detail].[ProductID] = product.productid) AS Sold_quantity, 
    (select sum(quantity) from [purchase order detail] where [purchase order detail].[ProductID] = product.productid) - (select sum(quantity) from [order detail] where [order detail].[ProductID] = product.productid) AS Stock 
FROM Product 
ORDER BY Product.ProductName; 

Answer 2

這是你的查詢，這將使所需的輸出：

SELECT [Product].ProductName 
    ,SUM([Purchase Order Detail].Quantity) AS [Purchase Quantity] 
    ,[Order Detail].Quantity AS [Sales Quantity] 
FROM [Product] 
LEFT JOIN [Purchase Order Detail] ON [Product].ProductID = [Purchase Order Detail].ProductID 
LEFT JOIN (SELECT SUM(Quantity)as Quantity 
       ,[Order Detail].ProductID 
      FROM [Order Detail] 
      GROUP BY [Order Detail].ProductID 
     )AS [Order Detail] ON [Product].ProductID = [Order Detail].ProductID 
GROUP BY [Product].ProductName,[Order Detail].Quantity