[SQL] 프로그래머스 대여 횟수가 많은 자동차들의 월별 대여 횟수 구하기

문제 설명

다음은 어느 자동차 대여 회사의 자동차 대여 기록 정보를 담은 CAR_RENTAL_COMPANY_RENTAL_HISTORY 테이블입니다. 

CAR_RENTAL_COMPANY_RENTAL_HISTORY 테이블은 아래와 같은 구조로 되어있으며, HISTORY_ID, CAR_ID, START_DATE, END_DATE 는 각각 자동차 대여 기록 ID, 자동차 ID, 대여 시작일, 대여 종료일을 나타냅니다.

Column name	Type	Nullable
HISTORY_ID	INTEGER	FALSE
CAR_ID	INTEGER	FALSE
START_DATE	DATE	FALSE
END_DATE	DATE	FALSE

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.

 

https://school.programmers.co.kr/learn/courses/30/lessons/151139

프로그래머스

예시

예를 들어 CAR_RENTAL_COMPANY_RENTAL_HISTORY 테이블이 다음과 같다면

HISTORY_ID	CAR_ID	START_DATE	END_DATE
1	1	2022-07-27	2022-08-02
2	1	2022-08-03	2022-08-04
3	2	2022-08-05	2022-08-05
4	2	2022-08-09	2022-08-12
5	3	2022-09-16	2022-10-15
6	1	2022-08-24	2022-08-30
7	3	2022-10-16	2022-10-19
8	1	2022-09-03	2022-09-07
9	1	2022-09-18	2022-09-19
10	2	2022-09-08	2022-09-10
11	2	2022-10-16	2022-10-19
12	1	2022-09-29	2022-10-06
13	2	2022-10-30	2022-11-01
14	2	2022-11-05	2022-11-05
15	3	2022-11-11	2022-11-11

대여 시작일을 기준으로 총 대여 횟수가 5회 이상인 자동차는 자동차 ID가 1, 2인 자동차입니다. 

월 별 자동차 ID별 총 대여 횟수를 구하고 월 오름차순, 자동차 ID 내림차순으로 정렬하면 다음과 같이 나와야 합니다.

MONTH	CAR_ID	RECORDS
8	2	2
8	1	2
9	2	1
9	1	3
10	2	2

문제 풀이

1. 기간 내 총 대여 횟수가 5회 이상인 car_id 구하기

SELECT car_id
FROM car_rental_company_rental_history
WHERE start_date BETWEEN '2022-08-01' AND '2022-11-01'
GROUP BY car_id
HAVING COUNT(history_id) >= 5

2. 해당 car_id의 월별 대여 횟수 구하기

SELECT MONTH(start_date) AS month
     , car_id
     , COUNT(history_id) AS records
FROM car_rental_company_rental_history
WHERE start_date BETWEEN '2022-08-01' AND '2022-11-01'
      AND car_id IN (SELECT car_id
                     FROM car_rental_company_rental_history
                     WHERE start_date BETWEEN '2022-08-01' AND '2022-11-01'
                     GROUP BY car_id
                     HAVING COUNT(history_id) >= 5
                     )
GROUP BY month, car_id

3. 추가 조건 설정

1. 월 기준 오름차순 정렬, car_id 기준 내림차순 정렬

2. 특정 월의 총 대여 횟수가 0인 경우 제외

SELECT MONTH(start_date) AS month
     , car_id
     , COUNT(history_id) AS records
FROM car_rental_company_rental_history
WHERE start_date BETWEEN '2022-08-01' AND '2022-11-01'
      AND car_id IN (SELECT car_id
                     FROM car_rental_company_rental_history
                     WHERE start_date BETWEEN '2022-08-01' AND '2022-11-01'
                     GROUP BY car_id
                     HAVING COUNT(history_id) >= 5
                     )
GROUP BY month, car_id            
HAVING records > 0 
ORDER BY month ASC, car_id DESC;

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SQL을 독학하시는 분들에게 도움이 되길 바라며,

혹 더 좋은 방법이 있거나 오류가 있다면 편하게 말씀 부탁드립니다.