SQL查詢中的多個SUM，包括LEFT JOIN

Question

我想顯示特定客戶的所有工作訂單，以及他欠我們的款項。

我的問題是，在當前查詢中，一旦有一個以上的產品（“ Work_Order_Products”表），乘以“ Work_Order_Products”表返回的記錄數即可。

有辦法解決這個問題嗎？ 謝謝

SELECT
    W.ID_WorkOrder AS ID_WorkOrder,
    W.Number AS Number,
    W.Date AS Date,
    C.Name AS Name,
    SUM(WOP.Quantity * WOP.Price) AS totProducts,
    SUM(WOI.Times) AS totTimes
FROM Work_Order W
LEFT JOIN Work_Order_Products WOP ON WOP.ID_WorkOrder = W.ID_WorkOrder
LEFT JOIN Work_Order_Instructions WOI ON WOI.ID_WorkOrder = W.ID_WorkOrder
LEFT JOIN Customers C ON C.ID_WorkOrder = W.ID_Customer
WHERE W.ID_Customer = x
GROUP BY
    ID_WorkOrder,
    Number,
    Date,
    Name

Answer 1

我會嘗試相關子查詢而不是SUM：

更換：

SUM(WOI.Times) AS totTimes

有：

(
    select SUM(WOI.Times) from Work_Order_Instructions WOI
    where
        WOI.ID_WorkOrder = W.ID_WorkOrder

) as totTimes

Answer 2

按照克里斯的建議，這可能會起作用：

SELECT
    W.ID_WorkOrder AS ID_WorkOrder,
    W.Number AS Number,
    W.Date AS Date,
    C.Name AS Name,
    products.ProductCount AS totProducts,
    Instructions.totTimes AS totTimes
FROM Work_Order W
    LEFT JOIN
        (SELECT WOP.ID_WorkOrder, SUM(WOP.Quantity * WOP.Price) AS ProductCount
        FROM Work_Order_Products WOP
        GROUP BY WOP.ID_WorkOrder) AS products
    ON  products.ID_WorkOrder = W.ID_WorkOrder
    LEFT JOIN
        (SELECT WOI.ID_WorkOrder, SUM(WOI.Times) AS totTimes
        FROM Work_Order_Instructions WOI
        GROUP BY WOI.ID_WorkOrder) AS Instructions
    ON Instructions.ID_WorkOrder = W.ID_WorkOrder
    LEFT JOIN Customers C ON C.ID_WorkOrder = W.ID_Customer
WHERE W.ID_Customer = x
GROUP BY
    W.ID_WorkOrder,
    Number,
    Date,
    Name

也就是說，使用括號來創建“子表”，這將需要它們自己的別名。 （這里可能存在語法錯誤。當然，我沒有運行此數據。）

Answer 3

為了避免使用Work_Order_Products或Work_Order_Instructions表中的Work_Order_Instructions ，請在加入表之前處理匯總。

SELECT
  W.ID_WorkOrder AS ID_WorkOrder
 ,W.Number AS Number
 ,W.Date AS Date
 ,C.Name AS Name
 ,WOP.totProducts
 ,WOI.totTimes
FROM
  Work_Order AS W
LEFT JOIN
  (
    SELECT 
      ID_WorkOrder
      ,SUM(Quantity * Price) AS totProducts
    FROM
      Work_Order_Products
    GROUP BY
      ID_WorkOrder

  ) AS WOP
    ON
    WOP.ID_WorkOrder = W.ID_WorkOrder
LEFT JOIN
  (
    SELECT 
      ID_WorkOrder
      ,SUM(Times) AS totTimes
    FROM
      Work_Order_Instructions
    GROUP BY
      ID_WorkOrder
  ) AS WOI
    ON
    WOI.ID_WorkOrder = W.ID_WorkOrder
LEFT JOIN
  Customers AS C
    ON
    C.ID_WorkOrder = W.ID_Customer
WHERE
  W.ID_Customer = x;