chuck_nr.sql

with recursive
-- all friends into one direction
friends (a, b) as ( 
  values('Alice','Bob'), ('Alice','Carol'), ('Carol','Grace'), 
  ('Carol','Chuck'), ('Chuck','Grace'),('Chuck','Anne'),
  ('Bob','Dan'),('Dan','Anne'),('Eve','Adam')
), 
-- all friendships into both directions
friendship (name, friend) as (
  select a, b 
  from friends
  union all 
  select b, a 
  from friends
),

chuck_nr (name, nr) as (
  select 'Chuck', 0
  union 
  select f.name, c.nr + 1
  from chuck_nr c, friendship f
  where c.name = f.friend
  and c.nr < 3
  and f.name not in (select t.name from chuck_nr t where t.nr < 2)
)

select name, min(nr)
from chuck_nr
group by name