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

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