with rec (id, parent_id, [relat]) as (
  select
      id, parent_id, 0 as relat
   from employee_staff
  union all
    select ef.id, ef.parent_id, r.relat + 1 as relat
    from
      employee_staff ef
      INNER JOIN rec r on ef.parent_id = r.id
 )
select id, parent_id, max(relat) from rec GROUP BY id, parent_id