[Programmers] SQL 고득점 Kit - GROUP BY

고양이와 개는 몇 마리 있을까

MySQL / Oracle

SELECT ANIMAL_TYPE, COUNT(ANIMAL_TYPE) 
  FROM ANIMAL_INS
 GROUP BY ANIMAL_TYPE
 ORDER BY ANIMAL_TYPE ASC

동명 동물 수 찾기

MySQL / Oracle

SELECT NAME, COUNT(NAME) NM_COUNT 
  FROM ANIMAL_INS
 GROUP BY NAME
HAVING COUNT(NAME) > 1
 ORDER BY NAME ASC

입양 시각 구하기(1)

MySQL

SELECT HOUR(DATETIME), COUNT(*) 
  FROM ANIMAL_OUTS
 WHERE HOUR(DATETIME) BETWEEN 9 AND 19
 GROUP BY HOUR(DATETIME)
 ORDER BY HOUR(DATETIME) ASC

Oracle

SELECT EXTRACT(HOUR FROM CAST(DATETIME AS TIMESTAMP)), COUNT(*) 
  FROM ANIMAL_OUTS
 WHERE EXTRACT(HOUR FROM CAST(DATETIME AS TIMESTAMP)) BETWEEN 9 AND 19
 GROUP BY EXTRACT(HOUR FROM CAST(DATETIME AS TIMESTAMP))
 ORDER BY EXTRACT(HOUR FROM CAST(DATETIME AS TIMESTAMP)) ASC

입양 시각 구하기(2)