select dt,count(*) as dau, round(sum(new_in = dt)/count(*),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)a
join(select uid,min(date(in_time))as new_in from tb_user_log group by uid)b using (uid)
group by dt
order by dt

算逻辑表达式时不要习惯性用count