SQL solution using subquery
Code
# Code
```mysql []
# Write your MySQL query statement below
SELECT ROUND(
    COUNT(DISTINCT player_id) / 
    (SELECT COUNT(DISTINCT player_id) 
    FROM Activity)
    ,2) AS fraction
FROM Activity
WHERE (player_id, DATE_SUB(event_date, INTERVAL 1 DAY)) IN (
    SELECT player_id, MIN(event_date) AS first_login 
    FROM Activity 
    GROUP BY player_id
);
```
['MySQL']