使用SUM和INNER JOIN的SQL問題

Question

當我嘗試執行以下所示的查詢時出現此錯誤

在選擇列表中，列“ dbo.Stock_Purchase.Supplier_ID”無效，因為它既不包含在聚合函數中，也不包含在GROUP BY子句中。

查詢：

SELECT  
    dbo.Stock_Purchase.*, dbo.Stock_Purchase_Details.*, 
    dbo.Supplier.*,
    SUM(Stock_Purchase_Details.Discount) AS totaldis
FROM    
    dbo.Stock_Purchase 
INNER JOIN
    dbo.Stock_Purchase_Details ON dbo.Stock_Purchase.Purchase_ID = dbo.Stock_Purchase_Details.Purchase_ID 
INNER JOIN
    dbo.Supplier ON dbo.Stock_Purchase.Supplier_ID = dbo.Supplier.Supplier_ID 
GROUP BY
    Stock_Purchase.Purchase_ID 

Answer 1

您只能在GROUP BY中將該列包括為SELECT的“裸露”列。 所以：

SELECT p.Purchase_ID, sum(pd.Discount) as totaldis
FROM dbo.Stock_Purchase p INNER JOIN
     dbo.Stock_Purchase_Details pd
     ON p.Purchase_ID = pd.Purchase_ID INNER JOIN
     dbo.Supplier s
     ON p.Supplier_ID = s.Supplier_ID
GROUP BY p.Purchase_ID ;

還要注意表別名如何使查詢更易於閱讀，編寫和理解。

如果確實需要所有詳細信息，則可以使用窗口功能：

SELECT p.*, pd.*, s.*,
       SUM(pd.Discount) OVER (PARTITION BY p.Purchase_ID) as totaldis
FROM dbo.Stock_Purchase p INNER JOIN
     dbo.Stock_Purchase_Details pd
     ON p.Purchase_ID = pd.Purchase_ID INNER JOIN
     dbo.Supplier s
     ON p.Supplier_ID = s.Supplier_ID;