Simplest SQL Solution
Code\n\nSELECT ROUND(COUNT(a1.player_id)/(SELECT COUNT(DISTINCT player_id) FROM Activity), 2) AS fraction\nFROM Activity a1\nJOIN Activity a2\nWHERE a1.player_i
# Code\n```\nSELECT ROUND(COUNT(a1.player_id)/(SELECT COUNT(DISTINCT player_id) FROM Activity), 2) AS fraction\nFROM Activity a1\nJOIN Activity a2\nWHERE a1.player_id = a2.player_id\n    AND \n    (a1.player_id, a1.event_date) IN (\n    SELECT player_id, MIN(event_date) \n    FROM Activity\n    GROUP BY player_id) \n    AND DATEDIFF(a2.event_date, a1.event_date) = 1\n```
['MySQL']