SELECT CAR_ID, ROUND(AVG(DATEDIFF(END_DATE, START_DATE)+1), 1) AS AVERAGE_DURATION FROM CAR_RENTAL_COMPANY_RENTAL_HISTORY
GROUP BY CAR_ID
HAVING AVG(DATEDIFF(END_DATE, START_DATE) + 1) >= 7
ORDER BY AVERAGE_DURATION DESC, CAR_ID DESC
DATEDIFF()
두개의 날짜값의 차이를 int로 반환하는 Mssql 내장함수
SELECT DATEDIFF('구분자','Start_Date','End_Date')
ex) 2018년의 날짜구하기
SELECT DATEDIFF(dd,'2018-01-01','2018-12-31') + 1
구분자 종류