문제 설명 예시 해결 SELECT NAME, DATETIME FROM ANIMAL_INS WHERE ANIMAL_ID NOT IN (SELECT ANIMAL_ID FROM ANIMAL_OUTS) ORDER BY DATETIME LIMIT 3; SELECT A.NAME, A.DATETIME FROM ANIMAL_INS A LEFT JOIN ANIMAL_OUTS B ON A.ANIMAL_ID = B.ANIMAL_ID WHERE B.ANIMAL_ID IS NULL ORDER BY A.DATETIME LIMIT 3;