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(author_id) as num 
from (
    select author_id
    from (
        select distinct author_id,issue_type
        from issue_tb i
        right join answer_tb a 
        on i.issue_id=a.issue_id
        where issue_type in('Education','Career')
        ) ia
    group by author_id
    having count(author_id) =2
    ) counts