1045. Customers Who Bought All Products
SQL 50 · Sorting and Grouping (day 4). Decode it with the hints, solve it on LeetCode, then compare with the reference solution in MySQLPostgreSQL.
Your work
Hints
Open one at a time. Try to finish with as few as you can.
1. What does one output row represent?
One customer.
2. Approach
GROUP BY customer_id HAVING COUNT(DISTINCT product_key) = (SELECT COUNT(*) FROM Product).
3. The trap
DISTINCT matters: buying one product twice isn’t two products.
Reference solution
Tested on MySQL 8.0 and PostgreSQL 16. Switch dialect at the top of the page.
Show the MySQLPostgreSQL solution
SELECT customer_id
FROM Customer
GROUP BY customer_id
HAVING COUNT(DISTINCT product_key) = (SELECT COUNT(*) FROM Product);