SELECT article_id, title, coincidence FROM
(SELECT article_id,
       COUNT(article_id) as coincidence FROM
(SELECT t2.article_id, t2.tag_id FROM articles as t1
JOIN tags_to_articles as t2
ON tag_id IN
(SELECT t2.tag_id from articles as t2
JOIN tags_to_articles as t3
ON t2.id = t3.article_id
WHERE t1.id = 1)
WHERE t2.article_id != 1) t4
JOIN articles on articles.id = t4.article_id
GROUP BY article_id) t5
JOIN articles as t6 on t6.id = article_id
ORDER BY coincidence DESC