How can I calculate the time between registration to first time deposit?

You want to know what is the time, in days, that has past from a certain user's signup to their first deposit.

select avg(time_between_in_days) time_between_in_days  from 
(select customer_user_id ,su_date,ftd_date ,datediff(  ftd_date,su_date) as time_between_in_days from accounts)  
 
Segentation
Acquisition