SQL Query for counting number of orders per customer and Total Dollar amount

ms-access, sql

Solution

You would use `COUNT(DISTINCT ...)` in other SQL engines:

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

Which Access unfortunately does not support. Instead you can first get the Order dollar amounts and then join them before figuring the order counts:

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

If you need to include Customers that have orders with no items (unusual but possible), change `INNER JOIN` to `LEFT OUTER JOIN`.

Problem

I have two tables `Order` with columns: ``` OrderID,OrderDate,CID,EmployeeID ``` And `OrderItem` with columns: ``` OrderID,ItemID,Quantity,SalePrice ``` I need to return the CustomerID(CID), number of orders per customer, and each customers total amount for all orders. So far I have two separate queries. One gives me the count of customer orders.... ``` SELECT CID, Count(Order.OrderID) AS TotalOrders FROM [Order] Where CID = CID GROUP BY CID Order BY Count(Order.OrderID) DESC; ``` And the other gives me the total sales. I'm having trouble combining them... ``` SELECT CID, Sum(OrderItem.Quantity*OrderItem.SalePrice) AS TotalDollarAmount FROM OrderItem, [Order] WHERE OrderItem.OrderID = [Order].OrderID GROUP BY CID ``` I'm doing this in Access 2010.

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