1064 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 ') order by products_price' at line 1
in:
[SELECT p.`products_price`,p2c.`categories_id` FROM products p,products_to_categories p2c WHERE p2c.products_id=p.products_id AND ( p2c.categories_id = ) order by products_price]