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#
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 C.author_id) FROM ( SELECT B1.author_id FROM issue_tb A1 LEFT JOIN answer_tb B1 ON A1.issue_id = B1.issue_id where issue_type IN( 'Education') )C INNER JOIN ( SELECT B2.author_id FROM issue_tb A2 LEFT JOIN answer_tb B2 ON A2.issue_id = B2.issue_id WHERE A2.issue_type IN( 'Career') )D WHERE C.author_id = D.author_id
(1)统计回答过教育类问题的用户
- [条件]:where issue_type = 'Education'
(2)统计回答回答过职场类问题的用户
- [条件]:where issue_type = 'Career'
(3)取2段查询结果的交集,并进行去重计数
- COUNT(DISTINCT C.author_id)