【SQL0001】Query from the result of another query

Query from the result of another query .

• basic table

select * from Customers;select * from [Order Details];select * from Orders;

• first query

select o.CustomerID,sum(od.UnitPrice*od.Quality) as Amountfrom Orders o, [Order Details] odwhere o.OrderID = od.OrderID group by o.CustomerID ;

• secong query based on first query

select Avg(temp.Amount) as average from (select sum(od.UnitPrice*od.Quality) as Amountfrom Orders o, [Order Details] odwhere o.OrderID = od.OrderID group by o.CustomerID ) as temp;