How to join 2 tables when calling a count on the second table
select coaches.user_id, coalesce(counted.cnt,0) cnt
from coaches
left join (select count(coach_id) cnt, coach_id 
           from coach_assignments 
           where deleted_at is not null 
           group by coach_id) as counted
     on coaches.user_id = counted.coach_id
order by 2 asc