Databases · Junior · Question 23 of 75

How do you find users who have no orders?

1INNER JOIN orders o ON o.user_id = u.id WHERE o.id IS NULL
✓Correct answer: LEFT JOIN orders o ON o.user_id = u.id WHERE o.id IS NULL (or WHERE NOT EXISTS (...))
3SELECT * FROM users WHERE orders = 0

Explanation

This is an 'anti-join'. NOT EXISTS expresses it directly and the planner handles both forms well.

Further reading

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