Hàm & Gom nhóm

-- Get the month from order_date
SELECT ___(___ FROM ___) AS order_month, 
    p.pizza_size, 
    -- Calculate revenue
    ___(p.price * od.quantity) AS revenue
FROM orders o
INNER JOIN order_details od USING(order_id)
INNER JOIN pizzas p USING(pizza_id)
-- Appropriately group the query
___
-- Sort by revenue in descending order
___