default setting of sorting in drupal7

Default setting of sorting


function blog_list_view($form, &$form_state) {
    global $base_url;
    if (isset($form_state['values']['option'])) {
        $option = $form_state['values']['option'];
    }

    $html = '<div class="row-fluid"><div class="span12">'
            . '<a style="color:#0088CC;text-decoration:none;" href="' . $base_url . '/node/add/blog">Create New Blog</a>'
            . '<a style="color:#0088CC;text-decoration:none; padding-left:20px;" href="' . $base_url . '/admin/content/comment">Manage Comments</a>' .
            '</div></div>';
    $form['option'] = array(
        '#type' => 'markup',
        '#default_value' => $option,
        '#prefix' => $html,
//        '#suffix' => '</div>',
        '#attributes' => array('class' => array('input-medium')),
    );

    $header = array(
        array(
            'data' => 'Title',
            'field' => 'title'
        ),
        array(
            'data' => 'Author',
            'field' => 'uid'
        ),
        array(
            'data' => 'Updated',
            'field' => 'created'
        ),
        array(
            'data' => 'operations',
        ),
    );
    if (isset($_GET ['sort']) && isset($_GET ['order'])) {
        if ($_GET ['sort'] == 'asc')
            $sort = 'ASC';
        else
            $sort = 'DESC';

        switch ($_GET ['order']) {
            case 'Id' :
                $order = 'nid';
                break;
            case 'Title' :
                $order = 'title';
                break;
            case 'Author' :
                $order = 'uid';
                break;
            case 'Updated' :
                $order = 'changed';
                break;
        }
    } else {
        $sort = 'ASC';
        $order = 'nid';
    }


    $query = db_select('node', 'n');
    $query->join('users', 'u', 'u.uid=n.uid');
    $query->fields('n', array('title', 'nid', 'uid', 'changed'));
    $query->fields('u', array('name'));
    $query->condition('n.status', 1);
    $query->condition('n.type', array(blog), 'IN');
  
    if(!isset($_GET ['order'])){
              $query->orderBy('n.created', 'DESC');
    }else{
//    $query->range(0, 10);
    $query->orderBy($order, $sort);
    }