[SQL/프로그래머스] 없어진 기록 찾기, OUTER JOIN

문제

문제 답안1(RIGHT OUTER JOIN)

SELECT 
    O.ANIMAL_ID,
    O.NAME
FROM ANIMAL_INS I
RIGHT OUTER JOIN ANIMAL_OUTS O
ON I.ANIMAL_ID = O.ANIMAL_ID
WHERE I.ANIMAL_ID IS NULL
ORDER BY O.ANIMAL_ID ASC

문제 답안2(LEFT OUTER JOIN)

SELECT 
    O.ANIMAL_ID,
    O.NAME
FROM ANIMAL_OUTS O
LEFT OUTER JOIN ANIMAL_INS I
ON I.ANIMAL_ID = O.ANIMAL_ID
WHERE I.ANIMAL_ID IS NULL
ORDER BY O.ANIMAL_ID ASC

주의해야 할 답안1

SELECT i.ANIMAL_ID, i.NAME
FROM ANIMAL_INS I
RIGHT OUTER JOIN ANIMAL_OUTS O
ON I.ANIMAL_ID = O.ANIMAL_ID
WHERE I.ANIMAL_ID IS NULL
ORDER BY ANIMAL_ID ASC

• 실행 결과 :

주의해야 할 답안2

SELECT o.ANIMAL_ID, o.NAME
FROM ANIMAL_INS I
RIGHT OUTER JOIN ANIMAL_OUTS O
ON I.ANIMAL_ID = O.ANIMAL_ID
WHERE I.ANIMAL_ID = 'NULL'
ORDER BY ANIMAL_ID ASC

• 실행 결과 :