SELECT wallMessage.message, wallMessage.author,
wallMessage.id,
`user`.name,
`user`.surname,
wallMessage.author,
wallMessage.`date`,
wallMessage.pulse
FROM wallMessage
JOIN (SELECT idOutgoing AS idFriend
FROM `myFriends`
WHERE idInput=6  AND STATUS = 1
UNION
SELECT idInput AS idFriend
FROM `myFriends`
WHERE idOutgoing=6  AND STATUS = 1) AS myFriendsOnly
ON wallMessage.author =  myFriendsOnly.idFriend
LEFT JOIN `user` ON `user`.id = wallMessage.author
WHERE wallMessage.author <> 6 or (CURRENT_TIMESTAMP - `wallMessage`.`date`) < TIMESTAMP( '0000-00-00 00:15:00')
GROUP BY `id`
ORDER BY `wallMessage`.`id` DESC limit 0, 15