LEFT JOIN keeps everyone in SQL
SQL interview exercise on Joins, difficulty 2 of 3. Solve it in the editor beside a worked example, or cold in Interview mode with the example hidden; the tests run the moment you do.
Return every customer with the number of orders they have placed, 0 for customers who never ordered. Columns: name, orders. Most orders first, then by name.
Each exercise pairs a worked example with a twin problem to solve in a real editor; the tests run the moment you do. Interview mode hides the example: solve it from memory, without the hint or the solution, and it counts as solved cold. Progress is saved in your browser, and in your account if you sign in.