多对多sql select查询包含多个值，所有值都考虑在内

Question

There is the following database structure:

How do I write a query that returns only those Questions that have both CSS and JS tags?

Answer 1

You can use aggregation and having :

select tq.question_id
from tagsquestions tq join
     tags t
     on tq.tag_id = t.id
where t.name in ('JS', 'CSS')
group by tq.question_id
having count(*) = 2;

This assumes that the tags assigned to a single question are distinct. That seems like a reasonable assumption.