select date(t1.visit_time) as date
,concat(round(count(distinct t.user_id,date(t.order_time))/count(distinct t1.user_id,date(t1.visit_time))*100,1),'%') as cr
from visit_tb t1
left join order_tb t on t.user_id=t1.user_id and date(t.order_time) = date(t1.visit_time)
group by date(t1.visit_time)
order by date