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1. 없어진 기록 찾기
SELECT OUTS.ANIMAL_ID, OUTS.NAME
FROM ANIMAL_OUTS OUTS
LEFT OUTER JOIN ANIMAL_INS INS
ON OUTS.ANIMAL_ID = INS.ANIMAL_ID
WHERE INS.ANIMAL_ID IS NULL
ORDER BY INS.ANIMAL_ID
- OUTER JOIN : 기준이 되는 데이터 파악하여 LEFT/RIGHT 명시
- WHERE : 문제 조건 파악
2. 있었는데요 없었습니다
SELECT INS.ANIMAL_ID, INS.NAME
FROM ANIMAL_INS INS
LEFT OUTER JOIN ANIMAL_OUTS OUTS
ON INS.ANIMAL_ID = OUTS.ANIMAL_ID
WHERE INS.DATETIME > OUTS.DATETIME
ORDER BY INS.DATETIME
3. 오랜 기간 보호한 동물(1)
SELECT INS.NAME, INS.DATETIME
FROM ANIMAL_INS INS
LEFT OUTER JOIN ANIMAL_OUTS OUTS
ON INS.ANIMAL_ID = OUTS.ANIMAL_ID
WHERE OUTS.ANIMAL_ID IS NULL
ORDER BY INS.DATETIME
LIMIT 3