怎么写这个SQL语句？

Question

表people和posts，是一对多的关系，posts表
字段id、person_id、title
从posts表中查找同时发表过标题为“java","ruby","python"文章的person_id，不要求是模糊查询。

Answer 1

select person_id from
(select distinct person_id,title from posts where title in('java','ruby','python')) as t1
group by person_id having count(title)>2

环境：MySQL5.1