SQL · Reading data

distinct on

PostgreSQL keeps the first row per key according to the ORDER BY. SQLite does not support it.

sqlRunnable example sql course

Syntax

select distinct on (key) …

Example

Open in the lab

-- PostgreSQL only
-- SELECT DISTINCT ON (course_id) * FROM lessons ORDER BY course_id, updated_at DESC;

Reference pages are the quick answer. The course explains the why, shows the full example and ends with a challenge.