题解 | #异常的邮件概率#
异常的邮件概率
https://www.nowcoder.com/practice/d6dd656483b545159d3aa89b4c26004e
写个不连表的，我的习惯一般首先考虑子查询再考虑连表，所以这个的第一思路就是：想要正常的用户，那我构造一个都是正常用户的表不就好了，通常构造新表也是常用思路之一
select
date,
round(sum(case when type='no_completed'then 1 else 0 end)/count(1),3) p
from
(select type,date
from email
where send_id not in (select id from user where is_blacklist=1)
and receive_id not in (select id from user where is_blacklist=1))t1
group by date
order by date asc
