[LeetCode] 550. Game Play Analysis IV

 

 

[문제]

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[MySQL]

WITH first_event AS (
    SELECT player_id
         , MIN(event_date) AS first_date
    FROM Activity
    GROUP BY player_id
)

SELECT ROUND(COUNT(DISTINCT CASE WHEN a.event_date = DATE_ADD(f.first_date, INTERVAL 1 DAY) THEN a.player_id END) / COUNT(DISTINCT a.player_id), 2) AS fraction
FROM Activity AS a
    INNER JOIN first_event AS f ON a.player_id = f.player_id