tracing db error

[eluser]dwlamb[/eluser]
Hello,

I'm new to CI and trying to get the basics down after looking at some tutorials. For now,
I'm doing things by rote.

I have the following in a controller.

Code:

class Main extends CI_Controller {

    public function index()
    {
        // Standard SQL Query
        $sql = "SELECT * FROM main";
        $data['query_sql'] = $this->db->query($sql);
        $this->load->view('main', $data);
    }
}

Then I have the following in a view.

Code:

<?php print_r($query_sql->result_array()); ?>

When I run the script I get an error. This is the abbreviated form (in blue just to make it distinct here):

Undefined property: Main::$db

Call to a member function query() on a non-object

I checked database.php and the information entered for the database is correct.

I'm at a loss to determine what's wrong for I am doing something simple that I was able to do in a tutorial and I'm certain I followed the steps.