with a as
(select date_format(order_time,'%Y-%m-%d') as date,count(distinct user_id) as cnt1
from order_tb 
group by date_format(order_time,'%Y-%m-%d')),

b as (
    select date_format(visit_time,'%Y-%m-%d') as date,count(distinct user_id) as cnt2
    from visit_tb
    group by date_format(visit_time,'%Y-%m-%d')
)

select a.date,concat(ROUND(cnt1/cnt2* 100, 1),'%') as cr
from a
join b on a.date = b.date 

二刷 简单