Databases · Junior · Question 25 of 75

A user has 3 orders and 2 addresses. You join `users`, `orders` and `addresses` on `user_id`. How many rows do you get for that user?

15
✓Correct answer: 6
33

Explanation

Joining two independent one-to-many relations multiplies rows (3 × 2). Sums and counts over such a join are inflated; aggregate each relation separately.

A user has 3 orders and 2 addresses. You join `users`, `orders` and `addresses` on `user_id`. How many rows do you get for that user?

Explanation

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A user has 3 orders and 2 addresses. You join users, orders and addresses on user_id. How many rows do you get for that user?

Explanation

Further reading

Test yourself

A user has 3 orders and 2 addresses. You join `users`, `orders` and `addresses` on `user_id`. How many rows do you get for that user?