EasySubqueries & EXISTS

NOT EXISTS: customers who never ordered

The query

SQL

SELECT name, email, joined_at
FROM customers c
WHERE NOT EXISTS (
  SELECT 1
  FROM orders o
  WHERE o.cust_id = c.cust_id
)
ORDER BY joined_at DESC;

Tested against PostgreSQL 16

Note

“NOT EXISTS is usually faster than NOT IN when subquery result may include NULLs.