gistfile1.txt

      $q = 'select sum(op.products_quantity) as quantity
            from orders_products op
            join (
              select distinct orders_id
              from orders
              where orders_status in (1,5)
            ) o on o.orders_id = op.orders_id
            join (
              select distinct products_id
              from parts
              where parts_id = ' . $dbi->escape($this->id()) . '
            ) p on p.products_id = op.products_id';