database problem. Help me!

[eluser]java[/eluser]
I want to get value of 1 table via id of 2 table. I have tried to use join() query command to solve but it not effective and display this error:

An Error Was Encountered
Unable to load the requested language file: language/db_lang.php

This is my code:

Code:

$this->db->select('SoBaoDanh,HoTen,NgaySinh,DiaChi,ChieuCao,CanNang,VongNguc,VongEo,VongMong');
        //$this->db->select('Ten');// field name of another table
        $this->db->from('hoahau');
        $this->db->join('thanhpho','ThanhPhoID = ThanhPhoID');// join 2 table
        $this->db->where('Enable','1');
        $this->db->orderby('HoahauID desc');

How can i get the value of a table which have related with another table? Tell me please..