링크 : https://school.programmers.co.kr/learn/courses/30/lessons/59044 C> Q> H> - '입양을 가면 반대편 테이블에 적재된다' 라는 이해가 필요 - A- (A교집합B) 함수 적용 L&U> - 차집합 쓸 때 필요 Left join where is null A> SELECT T1.NAME , T1.DATETIME FROM ANIMAL_INS AS T1 LEFT JOIN ANIMAL_OUTS AS T2 ON T1.ANIMAL_ID = T2.ANIMAL_ID WHERE T2.ANIMAL_ID IS NULL ORDER BY 2 ASC LIMIT 3