Question

我试图通过编写查询以选择支出最高的前10名来确定客户的支出行为。

我有以下查询，它运行正常：

SELECT c.CustomerID
     , SUM(Quantity * UnitPrice) Total_Spent
  FROM Orders o
  JOIN OrderDetails d
    ON d.OrderID = o.OrderID 
  JOIN Customers c
    ON c.CustomerID = o.CustomerID 
 GROUP 
    BY c.CustomerID
 ORDER
    BY Total_Spent
 limit 10;

但是，我想创建一个子查询，而不要使用这个复杂的子查询。我已经尝试了以下方法，但是不起作用：

SELECT Customers.CustomerID
FROM Customers
JOIN (
    SELECT SUM(Quantity *UnitPrice) as Total_Spent
    FROM Orders
    JOIN OrderDetails
    ON Orders.OrderID = OrderDetails.OrderID) Orders
ON Orders.CustomerID = Customers.CustomerID
GROUP BY Customers.CustomerID
ORDER BY Total_Spent
LIMIT 10;

我不知道问题是什么。（我对SQL有点陌生）

Answer 1

您可以简化查询，因为不需要customers表。那和表别名应该使您的查询更简单：

SELECT o.CustomerID, SUM(od.Quantity * od.UnitPrice) as Total_Spent
FROM Orders o JOIN
     OrderDetails od
     ON o.OrderID = od.OrderID
GROUP BY o.CustomerID
ORDER BY Total_Spent DESC
LIMIT 10;

将SQL查询转换为子查询

1 个答案: