Faster than 82.38% : easy to understand MySQL solution, no cte needed
\nselect round(count(distinct a1.player_id)/(select count(distinct player_id) from activity),2) as fraction\nfrom activity a1 join (select player_id, min(event_
```\nselect round(count(distinct a1.player_id)/(select count(distinct player_id) from activity),2) as fraction\nfrom activity a1 join (select player_id, min(event_date) as event_date \n      from activity group by 1) a2\non a1.player_id = a2.player_id and datediff(a1.event_date,a2.event_date) =1;\n```
[]