Ordering items with matching tags by number of tags that match

Question

I\'m trying to figure out how to order items with matching tags by the number of tags that match.

Let\'s say you have three MySQL tables:

• tags(tag_id

Answer 1

Something resembling:

SELECT a.* 
FROM articles AS a 
INNER JOIN articles_tags AS at ON a.id=at.article_id
INNER JOIN tags AS t ON at.tag_id = t.id
WHERE t.title = 'funny' OR t.title = 'goofy' OR t.title = 'silly' AND a.id != 
GROUP BY a.id
ORDER BY COUNT(a.id) DESC

With just the usual indexes, assuming articles_tags has PK of (article_id, tag_id), and an index on tags.title