选择使用dense_rank，按用户id对date排名

with t1 as 
(
    select 
        date,
        ur.name as u_n,
        cl.name as c_n,
        dense_rank() over(partition by ur.id order by date desc)  as rk
    from 
        login       as lg 
        join user   as ur on ur.id = lg.user_id
        join client as cl on cl.id = lg.client_id
)
select 
    u_n,c_n,date
from t1 
where rk = 1
order by u_n asc