$sql = "INSERT INTO  " . DB_PREFIX . "product_special (`product_special_id`, `product_id`, `customer_group_id`, `priority`, `price`, `date_start`, `date_end`) VALUES (Null, '".$product_id."' , 8 , 1,'".$data["price"]."' , '".$data["kampanyabaslangic"]."' , '".$data["kampanyabitis"]."')"; 

$this->db->query($sql);