Question

I want to understand the relationship between a record being created in the users table and a user’s first purchase in the subscriptions table. Both tables have created_at as a field, and users.id=subscriptions.user_id.

I’d like output that groups a count of users and the amount of time (in days) between the day that they joined and the day they made their first purchase.

days, users
0, 45
1, 63
2, 14
3, 7

Answer 1

SELECT 
      days
    , COUNT(*) AS users
FROM
      ( SELECT
              DATEDIFF(MIN(s.created_at), u.created_at) AS days
        FROM 
              users AS u
          JOIN
              subscriptions  AS s
            ON
              s.user_id = u.id
        GROUP BY 
              u.id
      ) AS grp
GROUP BY 
      days