题解 | #异常的邮件概率#
异常的邮件概率
http://www.nowcoder.com/practice/d6dd656483b545159d3aa89b4c26004e
思路：send_id和receive_id都不在user中黑名单id里，用sum(if)/xounr(*)
select
date
,round(sum(if(type = 'no_completed',1,0))/count(*),3) p
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
)
group by date
order by date
sql刷题笔记 文章被收录于专栏
sql刷题笔记，有思路的讲解，不过比较简单，可以稍微启发你一下，留给你一些思考的空间。
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