문제

노선별 평균 역 사이 거리 조회하기

풀이

코드

SELECT route,
    CONCAT(ROUND(SUM(d_between_dist), 1), 'km') AS total_distance,
    CONCAT(ROUND(AVG(d_between_dist), 2), 'km') AS average_distance
FROM subway_distance
GROUP BY route
ORDER BY ROUND(SUM(d_between_dist), 1) DESC;

-- SELECT route,
--     CONCAT(ROUND(SUM(d_between_dist), 1), 'km') AS total_distance,
--     CONCAT(ROUND(AVG(d_between_dist), 2), 'km') AS average_distance
-- FROM subway_distance
-- GROUP BY route
-- ORDER BY total_distance DESC;

설명

문제에서 요구한 결과를 만들기 위해 쿼리에서 실제로 쓴 것들이다.

• GROUP BY 로 묶어서 집계
• ORDER BY 로 정렬 (내림차순 포함)
• 사용한 함수: AVG(), CONCAT(), ROUND(), SUM()