Question

I have a keywords and a categories table with an ID and a name col (I can’t merge them into a single table!)

There’s an articles table with ID, name, text.

And the many-to-many connection tables:

• ckw for keywords, columns: key_id, article_id

• ccat for categories, columns: cat_id, article_id

I can write a query to get those articles which belong to keywords ID 5 AND ID 7:

SELECT articles.name FROM articles
JOIN ckw ON (ckw.article_id = articles.id)
WHERE ckw.key_id IN (5, 7)
GROUP BY ckw.article_id
HAVING COUNT(ckw.key_id) = 2

But what if I want to get those articles which belong to keywords ID 5 AND ID 7, and also belong to category ID 12 AND ID 18? I can’t figure the right query out.

Answer 1

SELECT articles.name
FROM articles
inner JOIN ckw ON ckw.article_id = articles.id
inner join ccat on ccat.article_id = articles.id
WHERE ckw.key_id IN (5, 7) 
and ccat.category_id in (12,18)
GROUP BY articles.article_id , articles.name 
HAVING COUNT(distinct ckw.key_id) = 2 
and count(distinct ccat.category_id) = 2