select
    date(ot.order_time) as date,
    concat(round(count(distinct ot.user_id) / count(distinct vt.user_id) * 100,1),'%') as cr
from
    order_tb ot
left join
    visit_tb vt on date(ot.order_time) = date(vt.visit_time)
group by 
    1 
order by
    1