untested but...
If i where to write raw SQL, i think this is what you are asking for (where
auth.user.id==42):
SELECT ut.user, count(*)
FROM users_tags ut
WHERE ut.user != 42
AND ut.tag IN (SELECT tag FROM user_tags WHERE user=42)
GROUP BY ut.user
ORDER BY count(*)
and i think this translated to DAL is:
count = db.user_tags.id.count()
query = db((db.user_tags.user != auth.user.id) &
(db.user_tags.tag.belongs(db(db.user_tags.user==auth.user.id)._select())))
rows = query.select(db.user_tags.user,
count,
groupby=db.user_tags.user,
orderby=count)
as i said, untested, but following similar logic i had written before.
christian
