SQL per ottenere amici E amici di amici di un utente

SELECT f1.user_id, f1.friend_id FROM
friends_info f1
WHERE f1.user_id = 1 OR
f1.user_id IN
(
 select f2.friend_id
 from friends_info f2
 where f2.user_id = 1
)
 ORDER BY user_id