select
    user_id,
    sum(floor(timestampdiff(minute,visit_time,leave_time)/10)) as point
from 
    visit_tb
group by
    user_id
order by 
    point desc

向下取整

DIV或 FLOOR(x / 10)

向上取整

CEIL(x / 10)

四舍五入

ROUND(x / 10)