题解 | #回答过教育问题的用户里有多少用户回答过职场问题#

WITH t1 as(select tb2.*,tb1.issue_type
    from issue_tb tb1
    right join  answer_tb tb2
    on tb1.issue_id=tb2.issue_id),
t2 as(select distinct author_id ,  if(issue_type='Education',1,null) Education 
    from t1),
t3 as( select distinct author_id ,  if(issue_type='Career',1,null) Career 
    from t1)
select count(if(Education=1 and Career=1 ,1,null)) num from t3 
right join t2
on t2.author_id=t3.author_id