대여 횟수가 많은 자동차들의 월별 대여 횟수 구하기- 정답공유 및 단계 별 코딩 과정(PROGRAMMERS - SQL)

문제
CAR_RENTAL_COMPANY_RENTAL_HISTORY 테이블에서 대여 시작일을 기준으로 2022년 8월부터 2022년 10월까지 총 대여 횟수가 5회 이상인 자동차들에 대해서 해당 기간 동안의 월별 자동차 ID 별 총 대여 횟수(컬럼명: RECORDS) 리스트를 출력하는 SQL문을 작성해주세요. 결과는 월을 기준으로 오름차순 정렬하고, 월이 같다면 자동차 ID를 기준으로 내림차순 정렬해주세요. 특정 월의 총 대여 횟수가 0인 경우에는 결과에서 제외해주세요.

 

문제 링크 : 대여 횟수가 많은 자동차들의 월별 대여 횟수 구하기

 

작성답안

SELECT 
MONTH(START_DATE) AS MONTH,
CAR_ID,
COUNT(*) AS RECORDS
FROM CAR_RENTAL_COMPANY_RENTAL_HISTORY 
WHERE (START_DATE >= '2022-08-01' AND START_DATE <= '2022-11-01')
AND CAR_ID IN (SELECT 
                 CAR_ID
                 FROM CAR_RENTAL_COMPANY_RENTAL_HISTORY 

                 WHERE START_DATE >= '2022-08-01'
                   AND START_DATE <= '2022-11-01'

                GROUP BY CAR_ID
                HAVING COUNT(*)>=5)
GROUP BY MONTH,CAR_ID

ORDER BY MONTH, CAR_ID DESC;

 

단계 정리

STEP 1

• 8월과 10월 사이에 있는 CAR_ID 구하기

SELECT 
CAR_ID
FROM CAR_RENTAL_COMPANY_RENTAL_HISTORY 

WHERE START_DATE >= '2022-08-01'AND START_DATE <= '2022-11-01'

 

STEP 2

• CAR_ID기준으로 GROUP BY → 5번이상 RENT 개수

SELECT 
CAR_ID
FROM CAR_RENTAL_COMPANY_RENTAL_HISTORY 

WHERE START_DATE >= '2022-08-01'AND START_DATE <= '2022-11-01'

GROUP BY CAR_ID
HAVING COUNT(*)>=5

 

STEP 3

• STEP 1에서 구한 CAR_ID 중
• 조건 1 : 8월~10월사이
• 조건 2 : CAR_ID가 STEP 1에서 구한 CAR_ID안에 있어야함

WHERE (START_DATE >= '2022-08-01' AND START_DATE <= '2022-11-01')
AND CAR_ID IN (SELECT 
                 CAR_ID
                 FROM CAR_RENTAL_COMPANY_RENTAL_HISTORY 

                 WHERE START_DATE >= '2022-08-01'
                   AND START_DATE <= '2022-11-01'

                GROUP BY CAR_ID
                HAVING COUNT(*)>=5)

 

STEP 4

• 해당 기간 동안의 월별 자동차 ID 별 → GROUP BY MONTH,CAR_ID
• 월을 기준으로 오름차순 정렬하고, 월이 같다면 자동차 ID를 기준으로 내림차순 정렬 → ORDER BY MONTH ASC, CAR_ID DESC

WHERE (START_DATE >= '2022-08-01' AND START_DATE <= '2022-11-01')
AND CAR_ID IN (SELECT 
                 CAR_ID
                 FROM CAR_RENTAL_COMPANY_RENTAL_HISTORY 

                 WHERE START_DATE >= '2022-08-01'
                   AND START_DATE <= '2022-11-01'

                GROUP BY CAR_ID
                HAVING COUNT(*)>=5)
GROUP BY MONTH,CAR_ID
ORDER BY MONTH ASC, CAR_ID DESC;

 

STEP 5 - LAST

• 최종 결과 구하기
• MONTH : MONTH(START_DATE)
• CAR_ID
• RECORDS : COUNT(*) → 아래에 설정한 조건에 해당하는 모든 행 개수 계산

SELECT 
MONTH(START_DATE) AS MONTH,
CAR_ID,
COUNT(*) AS RECORDS
FROM CAR_RENTAL_COMPANY_RENTAL_HISTORY 
WHERE (START_DATE >= '2022-08-01' AND START_DATE <= '2022-11-01')
AND CAR_ID IN (SELECT 
                 CAR_ID
                 FROM CAR_RENTAL_COMPANY_RENTAL_HISTORY 

                 WHERE START_DATE >= '2022-08-01'
                   AND START_DATE <= '2022-11-01'

                GROUP BY CAR_ID
                HAVING COUNT(*)>=5)
GROUP BY MONTH,CAR_ID

ORDER BY MONTH, CAR_ID DESC;