1.先获取每一个用户最后登录日期的行数据 
select l.date from login l 
where
l.date in (SELECT MAX(l2.date) from login l2 where l.user_id=l2.user_id)
2.再根据行数据中的用户ID以及客户端ID子查询出对应的名称
3.最后根据用户名排序
SELECT 
 (select `name` from `user` u where u.id = l.user_id),
 (select `name` from client c where l.client_id = c.id),
 l.date 
 from login l
 left join `user`  u2 on  u2.id = l.user_id
 where
 l.date in (SELECT MAX(l2.date) from login l2 where l.user_id=l2.user_id)
 ORDER BY u2.name