Ver original(SELECT fo.nombre, fo.cod, us.nick FROM usuario us INNER JOIN fotos fo ON li.usuario = us.cod INNER JOIN Libro li ON li.cod = fo.libro WHERE li.cod = '448' AND fo.cod > 668 LIMIT 5) UNION (SELECT fo2.nombre, fo2.cod, us2.nick FROM usuario us2 INNER JOIN fotos fo2 ON li2.usuario = us2.cod INNER JOIN Libro li2 ON li2.cod = fo2.libro WHERE li2.cod = '448' AND fo2.cod <= 668 LIMIT 6)ORDER BY cod DESC