mysql solution
select  round(count(distinct player_id )/(select count(distinct player_id) from activity),2) as fraction\nfrom (\nselect player_id,event_date,\n       min(event
select  round(count(distinct player_id )/(select count(distinct player_id) from activity),2) as fraction\nfrom (\nselect player_id,event_date,\n       min(event_date) over (partition by player_id order by event_date) firstlog\n       from activity ) a\nwhere datediff(event_date,firstlog) = 1
['MySQL']