WordPress Custom Table Loop not quite right

I have this code on a wordpress si开发者_开发百科te, in a custom table. The page is here: http://ulsandbox.org/bbtb10/?page_id=183

<h1> 2009 Authors List</h1>
 <h3> Click on each author to read more about them</h3>
 <p>&nbsp;</p>
 <hr align="left" width="75%">
View Categories:<p><a href="#childrens">Childrens</a> | <a href="#fiction">Fiction</a> | <a href="#non-fiction">Non-Fiction</a> | <a href="#teen">Teen</a> | <a href="#other">Other</a></p>
<p>&nbsp;</p>

<?php

$results = $wpdb->get_results( 'SELECT author_sub9.Sid, author_sub9.author_lname, author_sub9.author_fname, author_sub9.title, author_sub9.genre, author_sub9.approved
FROM author_sub9
WHERE author_sub9.approved = 1
ORDER BY author_sub9.genre,author_sub9.author_lname', ARRAY_A );
 $sLastGenre='';
if ($results) {
foreach ($results as $Row)
  if ($Row['genre']!=$sLastGenre)
  {
    if ($sLastGenre != '')
 echo '<br /><a href="authordetail.php?recordID='.$Row['Sid'].'">'.$Row['author_lname'].'</a>'.','.$Row['author_fname'].'<br />';
    $sLastGenre=$Row['genre'];
  }

}



?>

As you can see I get:

Fatal error: Call to a member function get_results() on a non-object 

Have you added $wpdb as a global?

global $wpdb;

$wpdb->get_result($sql, ARRAY_A);