将两个不同表中的两列相乘后求最大值 - SQL

Question

I'm trying to find the right way to find the maximum after multiplying 2 columns in different tables: Orders (OID, PID, Quantity, Date) Products (PID, Pname, Price, Category, Subcategory) . I need to find which OID has the highest total order amount. I've tried this:

SELECT OID, OrderAmount
FROM Orders
WHERE OrderAmount=(SELECT MAX(OrderAmount) from Orders
(SELECT Orders.OID, OrderAmount=Products.Price*Orders.Quantity
FROM Orders
INNER JOIN Products ON Orders.PID=Products.PID); 

Maybe there is a more effective solution? Thanks all in advance!

Answer 1

Method 1: Aggregate function

SELECT TOP 1 OID, MAX(OrderAmount) MaxOrderAmount
FROM (
       SELECT Orders.OID, OrderAmount = Products.Price * Orders.Quantity
       FROM Orders INNER JOIN Products ON Orders.PID=Products.PID
     ) X GROUP BY OID

Method 1: Row_Number Concept

SELECT TOP 1 OID, OrderAmount AS MaxOrderAmount
FROM (
       SELECT Orders.OID, OrderAmount = Products.Price * Orders.Quantity
              ROW_NUMBER() OVER(ORDER BY Products.Price * Orders.Quantity) RN
       FROM Orders INNER JOIN Products ON Orders.PID=Products.PID
     ) X WHERE RN = 1