select a1.u_n, a1.c_n, a1.date from 
(select u.name as u_n
      ,c.name as c_n
      ,l.date as date
      ,row_number() over(partition by u.id order by date desc ) as num
from user u, client c, login l
where u.id = l.user_id and c.id = l.client_id) a1
where a1.num = 1
order by a1.u_n