With

with

with절 subquery가 너무 많아서 알아보기 힘들 때 사용 서브쿼리가 많아져서 지저분해 보임 select c.title, a.cnt_checkins, b.cnt_total, (a.cnt_checkins/b.cnt_total) as ratio from ( select course_id, count(distinct(user_id)) as cnt_checkins from checkins group by course_id ) a inner join ( select course_id, count(*) as cnt_total from orders group by course_id ) b on a.course_id = b.course_id inner join courses c on a.course_id = c...