Simple solution
Code\n\nselect round(sum(case when (select min(a1.event_date) from activity a1 where a1.player_id = a.player_id) + 1 = a.event_date then 1 else 0 end)/count(dis
# Code\n```\nselect round(sum(case when (select min(a1.event_date) from activity a1 where a1.player_id = a.player_id) + 1 = a.event_date then 1 else 0 end)/count(distinct a.player_id),2) as "fraction" \n  from activity a\n```
['Oracle']