select t1.dt,count(distinct t1.uid) as dau,
round(count(t2.uid)/count(distinct t1.uid),2) as uv_new_ratio
from
    (select uid,date(in_time) as dt
    from tb_user_log
    union
    select uid,date(out_time) as dt
    from tb_user_log
     ) as t1
left join 
    (select uid,min(date(in_time)) as min_time
     from tb_user_log
     group by uid
    )as t2
on t1.uid=t2.uid
and t1.dt=t2.min_time
group by t1.dt
order by t1.dt