The task is to find what fraction of total users have logged in at least for one more consecutive day after their first login.

SELECT 
    ROUND( COUNT( b.player_id )/COUNT( DISTINCT (SELECT a.player_id FROM Activity a) ), 2 ) AS fraction
FROM 
    Activity b
WHERE 
    (b.player_id, DATE_ADD(b.event_date, INTERVAL -1 DAY)) IN
(
    SELECT 
        player_id, MIN(event_date)
    FROM 
        Activity
    GROUP BY 
        player_id
)```

The table structure is as follows

Table: Activity

+--------------+---------+
| Column Name  | Type    |
+--------------+---------+
| player_id    | int     |
| device_id    | int     |
| event_date   | date    |
| games_played | int     |
+--------------+---------+

Activity table:
+-----------+-----------+------------+--------------+
| player_id | device_id | event_date | games_played |
+-----------+-----------+------------+--------------+
| 1         | 2         | 2016-03-01 | 5            |
| 1         | 2         | 2016-03-02 | 6            |
| 2         | 3         | 2017-06-25 | 1            |
| 3         | 1         | 2016-03-02 | 0            |
| 3         | 4         | 2018-07-03 | 5            |
+-----------+-----------+------------+--------------+

I'm using two aliases a and b for the same table for referring them.

• a is for the unfiltered table, because I need a count of all Distinct users.
• b is for the filtered table, where only those rows are included for which a condition is met.

Where am I doing it wrong?