Top 3 Products by Revenue

CREATE TABLE products (
    product_id   INT PRIMARY KEY,
    product_name VARCHAR(100) NOT NULL,
    category     VARCHAR(50)
);

CREATE TABLE order_items (
    item_id      INT PRIMARY KEY,
    product_id   INT NOT NULL,
    quantity     INT NOT NULL,
    unit_price   DECIMAL(10,2) NOT NULL
);

INSERT INTO products VALUES
(1, 'Laptop Pro',     'Electronics'),
(2, 'Wireless Mouse', 'Electronics'),
(3, 'Standing Desk',  'Furniture'),
(4, 'USB-C Hub',      'Electronics'),
(5, 'Ergonomic Chair','Furniture');

INSERT INTO order_items VALUES
(1, 1, 5,  1299.00),
(2, 1, 3,  1299.00),
(3, 2, 20,   29.99),
(4, 3, 2,   499.00),
(5, 4, 15,   49.99),
(6, 5, 4,   399.00),
(7, 2, 10,   29.99),
(8, 3, 8,   499.00),
(9, 1, 2,  1299.00);

1. JOIN products with order_items. SUM(quantity * unit_price) gives revenue. Use LIMIT 3.