select
    b.o_date as date,
    concat(round(b.cnt*100/a.cnt,1),'%') as cr
from
(
select
    date(visit_time) as vi_date,
    count(distinct user_id) as cnt
from
    visit_tb
group by
    date(visit_time)) a
join
(
    select
        date(order_time) as o_date,
        count(distinct user_id) as cnt
    from
        order_tb
    group by
        date(order_time)
) b on b.o_date=a.vi_date
order by  b.o_date