Drill 19: Recall — Window functions

SELECT course_slug, title, minutes,
       ROW_NUMBER() OVER (
         PARTITION BY course_slug ORDER BY minutes DESC
       ) AS rank_in_course,
       SUM(minutes) OVER (PARTITION BY course_slug) AS course_minutes,
       ROUND(AVG(minutes) OVER (PARTITION BY course_slug), 1) AS course_avg
FROM lessons
ORDER BY course_slug, rank_in_course;