Detta är ett svar:
$q = new Doctrine_RawSql();
$q->addComponent('t', 'Tag')
->select('{t.name}, {t.count}')
->from('(SELECT COUNT(*) as count, t.name,t.idtag
FROM Tag t
INNER JOIN Video_Has_Tag v USING(idTag)
GROUP BY v.idTag
ORDER BY count DESC
LIMIT 50) t')
->orderBy('name');