select min, check two days then count
\n# Code\n\nSELECT ROUND(COUNT(DISTINCT a.player_id)/\n        (SELECT COUNT(DISTINCT player_id) FROM Activity), 2) as fraction\nFROM activity AS a\nINNER JOIN\
\n# Code\n```\nSELECT ROUND(COUNT(DISTINCT a.player_id)/\n        (SELECT COUNT(DISTINCT player_id) FROM Activity), 2) as fraction\nFROM activity AS a\nINNER JOIN\n        (SELECT player_id, MIN(event_date) AS min_event_date \n        FROM Activity GROUP BY 1) as b\n  ON a.player_id = b.player_id\nWHERE\n  DATEDIFF(a.event_date, b.min_event_date) = 1\n```
['MySQL']