SQL查询，用于统计每个客户的订单数和总金额

Question

我有两个 Order带有列的表：

OrderID,OrderDate,CID,EmployeeID

并OrderItem带有列：

OrderID,ItemID,Quantity,SalePrice

我需要返回CustomerID（CID），每个客户的订单数以及所有订单的每个客户的总金额。

到目前为止，我有两个单独的查询。一个给了我客户订单的数量。

SELECT CID, Count(Order.OrderID) AS TotalOrders
FROM [Order]
Where CID = CID 
GROUP BY CID
Order BY Count(Order.OrderID) DESC;

另一个给了我总销售额。我在合并它们时遇到了麻烦…

SELECT CID, Sum(OrderItem.Quantity*OrderItem.SalePrice) AS TotalDollarAmount
FROM OrderItem, [Order]
WHERE OrderItem.OrderID = [Order].OrderID
GROUP BY CID

我正在Access 2010中执行此操作。

Answer 1

您将COUNT(DISTINCT ...)在其他SQL引擎中使用：

SELECT CID, 
       Count(DISTINCT O.OrderID) AS TotalOrders, 
       Sum(OI.Quantity*OI.SalePrice) AS TotalDollarAmount 
FROM [Order] O
INNER JOIN [OrderItem] OI
  ON O.OrderID = OI.OrderID
GROUP BY CID 
Order BY Count(DISTINCT O.OrderID) DESC

不幸的是，哪个Access不支持。相反，您可以先获取订单金额，然后在确定订单数量之前将它们加入：

SELECT CID,
       COUNT(Orders.OrderID) AS TotalOrders,
       SUM(OrderAmounts.DollarAmount) AS TotalDollarAmount
FROM [Orders]
INNER JOIN (SELECT OrderID, Sum(Quantity*SalePrice) AS DollarAmount 
      FROM OrderItems GROUP BY OrderID) AS OrderAmounts
  ON Orders.OrderID = OrderAmounts.OrderID
GROUP BY CID
ORDER BY Count(Orders.OrderID) DESC

如果您需要包括订单中没有商品的客户（非正常但可能），请更改INNER JOIN为LEFT OUTER JOIN。