Problem Statement

List Customers and Products Without a Sale Using the `UNION` operator, return one list containing customers who do not have an invoice and products that were not sold. The source screenshot supplies the `customer` and `product` tables. To make the missing sales relationship explicit, use this reconstructed invoice table: `invoice(id INT PRIMARY KEY, customer_id INT, product_id INT)` For every customer that has no matching `invoice.customer_id`, return `customer`, the customer id, and the customer name. For every product that has no matching `invoice.product_id`, return `product`, the product id, and the product name. Return the three columns in exactly this order: `item_type`, `id`, `name`. The order of rows does not matter. Schema `customer(id INT PRIMARY KEY, customer_name VARCHAR(255), city_id INT, customer_address VARCHAR(255), contact_person VARCHAR(255), email VARCHAR(128), phone VARCHAR(128))` `product(id INT PRIMARY KEY, product_name VARCHAR(255))` `invoice(id INT PRIMARY KEY,