문제 설명 예시 해결 WITH RECURSIVE CTE AS ( SELECT 0 AS NUM UNION ALL SELECT NUM+1 FROM CTE WHERE NUM < 23 ) SELECT CTE.NUM HOUR, IFNULL(A.입양횟수, 0) COUNT FROM CTE LEFT JOIN (SELECT HOUR(datetime) 시간대, COUNT(*) 입양횟수 FROM ANIMAL_OUTS GROUP BY 시간대 ORDER BY 시간대) A ON CTE.NUM = A.시간대;