Use MSSQL e MySQL com CodeIgniter

$active_group = "default";
$active_record = TRUE;

/*MYSQL DB config EXMPALE */
$db['default']['hostname'] = 'localhost';
$db['default']['username'] = 'username';
$db['default']['password'] = 'pass';
$db['default']['database'] = 'DATABASE_NAME';
$db['default']['dbdriver'] = 'mysqli';
//...


/* MSSQL DB config EXMPALE, note the first param my_mssql */

$db['my_mssql']['hostname'] = 'SQL SERVER IP';
$db['my_mssql']['username'] = 'username';
$db['my_mssql']['password'] = 'pass';
$db['my_mssql']['database'] = 'DATABASE_NAME';
$db['my_mssql']['dbdriver'] = 'mssql';
//...

class example_model extends CI_Model
{
    var $mssql;
    function __construct()
    {
        parent::__construct();
        $this->mssql = $this->load->database ( 'my_mssql', TRUE );
    }

    function get_some_mssql_rows(){
       //use $this->mssql instead of $this->db
       $query = $this->mssql->query('select * from mssql_table');
       //...
    }

    function get_some_mysql_rows(){
       //use  $this->db for default 
       $query = $this->db->query('select * from mysql_table');
       //...
    }
}