my-guitar-shop-database-exersices/Exercise_3.6.sql

SELECT 
    p.product_name,
    SUM((oi.item_price - oi.discount_amount) * oi.quantity) AS total_amount
FROM
    products p
        JOIN
    order_items oi ON p.product_id = oi.product_id
GROUP BY p.product_name ASC WITH ROLLUP;