NOT EXISTS

How can we find customers who have never placed an order?

Advanced⏱ 3 Minutes⭐ 1120 XP

🤔 THE QUESTION

How can we find customers who have never placed an order?

💡 WHAT IS IT?

NOT EXISTS returns true when the correlated subquery returns zero matching rows.

🎯 WHAT IS IT USED FOR?

Inactive customer targeting, zero-transaction auditing, missing reference detection.

💻 EXAMPLE

SELECT c.customer_name
FROM customers c
WHERE NOT EXISTS (
    SELECT 1
    FROM orders o
    WHERE o.customer_id = c.customer_id
);

Practice typing production-grade SQL code for NOT EXISTS.