Debugging: Duplicate Explosion in Join

This query overcounts revenue because of duplicate joins. Fix it. SELECT c.id, SUM(oi.quantity * oi.unit_price) AS revenue FROM customers c JOIN orders o ON c.id = o.customer_id JOIN order_items oi ON c.id = oi.order_id GROUP BY c.id;

customers(id), orders(id, customer_id), order_items(id, order_id, quantity, unit_price)