题解 | #回答过教育类问题的用户里回答过职场类问题的人数#
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
SELECT COUNT(DISTINCT author_id) AS num FROM ( -- 筛选出既回答过教育类又回答过职场类问题的用户 SELECT author_id FROM issue_tb JOIN answer_tb USING(issue_id) WHERE issue_type = 'Education' ) answer_edu JOIN ( SELECT author_id FROM issue_tb JOIN answer_tb USING(issue_id) WHERE issue_type = 'Career' ) answer_car USING(author_id)
