SELECT animal_type, count(*)
FROM animal_ins
Group BY animal_type
ORDER BY animal_type asc
SELECT name, count(*) as count
FROM animal_ins
Group BY name
HAVING 2 <= count(*)
ORDER BY name asc
SELECT name, count(name) as 'count'
FROM animal_ins
Group BY name
HAVING 2 <= count(name)
ORDER BY name asc
SELECT HOUR(datetime) as 'HOUR', COUNT(datetime) as 'COUNT'
FROM animal_outs
WHERE HOUR(datetime) BETWEEN '09:00:00' AND '19:59:00'
GROUP BY HOUR(datetime)
ORDER BY HOUR(datetime)
SET @변수명 = 할당할 값; -- '=' 기호를 사용하여 할당한다..!
-- 나중에 쓸 때
@변수명 := @변수명+2 as 컬럼명 -- ':=' 기호를 사용해야 한다 주의!
SET @HOUR = -1; -- @HOUR라는 변수 선언(시간은 0부터이므로)
SELECT (@HOUR := @HOUR+1) as 'HOUR'
FROM animal_outs
WHERE @HOUR <= 22;
서브쿼리 사용해야 함
그래서 스칼라 서브쿼리 안에서 @HOUR 만들어준게 HOUR(datetime)과 같은 것만 Count()수행
참고 링크 : https://jaaamj.tistory.com/155
정답 쿼리
SET @HOUR = -1; -- @HOUR라는 변수 선언(시간은 0부터이므로)
SELECT (@HOUR := @HOUR+1) as 'HOUR',
(SELECT COUNT(HOUR(datetime))
FROM animal_outs
WHERE HOUR(datetime) = @HOUR) as 'COUNT'
FROM animal_outs
WHERE @HOUR <= 22;