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#

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'