very newbie question

[eluser]Unknown[/eluser]
hey,
im new to php and codeigniter and i want to create something with ci.
here is my question, how can i create like this query

Code:

SELECT username,password FROM users WHERE username=$foo AND password=$bar

with codeigniter activerecord ? like this ?

Code:

$this->db->select('username,password');
$this->db->from('users');
$this->db->where('username', $foo);
$this->db->where('password', $bar);
$query = $this->db->get();

thanx form help.