力扣SQL第1633题

select r.contest_id,
round(count(r.user_id)/(select count(*) from Users)*100,2) percentage
from Users u 
right join Register r 
on u.user_id = r.user_id
group by contest_id
order by percentage desc,contest_id asc;

注意其中镶嵌的这个select语句，用来统计总的用户数