3065 - Expression #1 of ORDER BY clause is not in SELECT list, references column 'usr_ud04_237_5.p.products_ordered' which is not in SELECT list; this is incompatible with DISTINCT

select distinct p.products_id, pd.products_name from products p, products_description pd, products_to_categories p2c, categories c where p.products_status = '1' and p.products_ordered > 0 and p.products_id = pd.products_id and pd.language_id = '1' and p.products_id = p2c.products_id and p2c.categories_id = c.categories_id and '31' in (c.categories_id, c.parent_id) order by p.products_ordered desc, pd.products_name limit 6