We need a list of customer ids with the total amount they have ordered. Write a SQL statement to return customer id (cust_id in Orders table) and total_ordered using a subquery to return the total of orders for each customer. Sort the results by amount spent from greatest to the least. Hint, you’ve used the SUM() to calculate order totals previously.
SELECT cust_id, (SELECT SUM(item_price*quantity) FROM OrderItems WHERE Orders.order_num = OrderItems.order_num) AS total_ordered FROM Orders ORDER BY total_ordered DESC;