simple easy solution
SELECT round(count(distinct player_id)\n             /(SELECT count(distinct player_id) FROM activity),2) as fraction\nFROM activity\nWHERE (player_id, event_da
SELECT round(count(distinct player_id)\n             /(SELECT count(distinct player_id) FROM activity),2) as fraction\nFROM activity\nWHERE (player_id, event_date) IN \n    (SELECT player_id, DATE(min(event_date) + 1)\n    FROM activity\n    GROUP BY player_id)
['MySQL']