Fold rows into a list in SQL
SQL interview exercise on Strings, Dates & CASE, 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 each order with its product names as one comma-and-space separated list ('A, B'), alphabetical within the list. Columns: order_id, items. Sorted by order_id.
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.