MySQL error!

You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'AND depth > ) OR ( thread < )) ORDER BY thread DESC, depth ASC limit 1' at line 2(Errno=1064)

Your query:
SELECT num, title FROM mbb WHERE id='6' AND (( thread= AND depth > ) OR ( thread < )) ORDER BY thread DESC, depth ASC limit 1