SELECT GROUP_CONCAT(l2.friend_id) AS friends
FROM friends_friends l1
JOIN friends_friends l2
ON l2.user_id = l1.friend_id
WHERE l1.user_id = 503695576;
SELECT GROUP_CONCAT(l2.friend_id) AS friends
FROM friends_friends l1
JOIN friends_friends l2
ON l2.user_id = l1.friend_id
WHERE l1.user_id = 503695576;