hive-求每个用户最小时间的信息

u	datetime	action	dt

select t2.*
from
(select dt,u,min(datatime)
from tbl
where dt='2018-08-01'
group by dt,u)t1
join
(
select * from tbl
where dt='2018-08-01'
) t2
on t1.dt=t2.dt and t1.u=t2.u