[MySQL] solvesql 최고의 근무일을 찾아라

문제 

Waiter's Tips 데이터셋에는 식사 금액, 팁, 결제자 성별, 결제 요일 등 레스토랑 손님들의 계산 정보가 들어있습니다. 

이 레스토랑에 근무하는 서버는 팁을 많이 받을 수 있는 날 하루를 골라 근무하고 싶습니다.
요일별로 팁 총액을 집계하고 팁이 가장 많았던 요일과 그날의 팁 총액을 출력하는 쿼리를 작성해주세요. 

그날의 팁 총액은 소수점 셋째 자리에서 반올림하여 출력되도록 해주세요.
결과 데이터는 아래 컬럼을 포함해야 합니다.
day - 요일
tip_daily - 요일 별 팁 총액

 

https://solvesql.com/problems/best-working-day/

https://solvesql.com/problems/best-working-day/

문제 풀이

SELECT  day,
        ROUND(SUM(tip), 3) AS tip_daily
FROM    tips
GROUP BY day
ORDER BY tip_daily DESC
LIMIT 1;

SELECT day, tip_daily
FROM (
    SELECT  day,
            ROUND(SUM(tip), 3) AS tip_daily
    FROM    tips
    GROUP BY day
) AS tmp
ORDER BY tip_daily DESC
LIMIT 1;

WITH ranked_tips AS (
    SELECT day,
           ROUND(SUM(tip), 3) AS tip_daily,
           RANK() OVER (ORDER BY SUM(tip) DESC) AS rank
    FROM   tips
    GROUP BY day
)
SELECT day, tip_daily
FROM ranked_tips
WHERE rank = 1;

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SQL을 독학하시는 분들에게 도움이 되길 바라며,

혹 더 좋은 방법이 있거나 오류가 있다면 편하게 말씀 부탁드립니다.