Simple solution with no window function
\nselect round(count(distinct player_id) / (select count(distinct player_id) from Activity), 2) as \'fraction\'\nfrom Activity\nwhere (player_id, event_date) in
```\nselect round(count(distinct player_id) / (select count(distinct player_id) from Activity), 2) as \'fraction\'\nfrom Activity\nwhere (player_id, event_date) in (select player_id, date(min(event_date) + 1)  \n                   from Activity\n                   group by player_id)  \n```
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