출처

https://school.programmers.co.kr/learn/courses/30/lessons/59413

문제

풀이

WITH RECURSIVE TEMP AS (
    SELECT 0 AS H
    UNION ALL
    SELECT H + 1 FROM TEMP WHERE H < 23
)

SELECT
    H AS HOUR,
    COUNT(ANIMAL_ID) AS COUNT
FROM
    TEMP LEFT JOIN
    ANIMAL_OUTS ON H = HOUR(DATETIME)
GROUP BY H
ORDER BY H