题解 | #某乎问答回答过教育类问题的用户里有多少用户回答过职场类问题#
某乎问答回答过教育类问题的用户里有多少用户回答过职场类问题
http://www.nowcoder.com/practice/b02cf9ee7b9f4cdda308f8155ff3415d
select count(distinct author_id)
from answer_tb ans LEFT join issue_tb iss using(issue_id)
where author_id in (select author_id from answer_tb ans
LEFT join issue_tb iss using(issue_id)
where issue_type='Education')
and issue_type='Career'
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