[Programmers] 025 - 입양 시각 구하기(2)

  WITH RECURSIVE HOURS AS (
    SELECT 0 AS HOUR
    UNION ALL
    SELECT HOUR + 1
      FROM HOURS
     WHERE HOUR < 23
)
SELECT HOUR
     , COUNT(B.ANIMAL_ID)
  FROM HOURS A
  LEFT JOIN ANIMAL_OUTS B ON A.HOUR = HOUR(B.DATETIME)
 GROUP BY HOUR
 ORDER BY HOUR