[프로그래머스] 입양시간 구하기(2)_ORACLE

문제링크 : https://programmers.co.kr/learn/courses/30/lessons/59413

코딩테스트 연습 - 입양 시각 구하기(2)

 

--ORACLE 1
SELECT HOUR, COUNT(B.DATETIME) AS COUNT
FROM
(
    SELECT LEVEL-1 AS HOUR
    FROM DUAL 
    CONNECT BY LEVEL<=24
)A LEFT JOIN ANIMAL_OUTS B
ON A.HOUR = TO_CHAR(B.DATETIME,'HH24')
GROUP BY HOUR
ORDER BY HOUR;

--ORACLE 2
SELECT HOUR, COUNT(B.DATETIME) AS COUNT
FROM
(
    SELECT LEVEL-1 AS HOUR
    FROM DUAL 
    CONNECT BY LEVEL<=24
)A, ANIMAL_OUTS B
WHERE A.HOUR = TO_CHAR(B.DATETIME(+),'HH24')
GROUP BY HOUR
ORDER BY HOUR;