https://school.programmers.co.kr/learn/courses/30/lessons/59043
#outs DATETIME이 ins DATETIME 보다 빠른 경우 출력
SELECT
ins.ANIMAL_ID,
ins.NAME
FROM
ANIMAL_INS ins
INNER JOIN ANIMAL_OUTS outs
ON ins.ANIMAL_ID=outs.ANIMAL_ID
WHERE 1=1
AND outs.DATETIME<ins.DATETIME
ORDER BY
ins.DATETIME
아주 쉽다