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
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
https://www.nowcoder.com/practice/b02cf9ee7b9f4cdda308f8155ff3415d
同时满足两个的问题，可以用in再加个and
select count(a.author_id) num
from answer_tb a join issue_tb i
on a.issue_id = i.issue_id
where a.author_id in
(select a.author_id id
from answer_tb a join issue_tb i
on a.issue_id = i.issue_id
where i.issue_type = 'Education')
and i.issue_type = 'Career'
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