WordPress database error after upgrade

What I don’t understand: why do you have that complicated code instead of using just the template tags that would display your links?
Any rational explanation?

Please take into account that I do not have any knowledge of php or wordpress templates – I picked this template up a few years ago and as to the complicated code, well I can’t comment, that’s how it came, it all looks complicated to me. What should I replace it with? Template tags does not mean much to me – can I go somewhere and copy the necessary code?

Thanks

ok,

i’ve removed the following code from the sidebar and the error has disappeared – so it must definately be this piece of code causing the error:

<?php
 $link_cats = $wpdb->get_results("SELECT cat_id, cat_name FROM $wpdb->linkcategories");
 foreach ($link_cats as $link_cat) {
 ?>
  <li id="linkcat-<?php echo $link_cat->cat_id; ?>"><h4><?php echo $link_cat->cat_name; ?></h4>
   <ul>
    <?php wp_get_links($link_cat->cat_id); ?>
   </ul>
  </li>
 <?php } ?>

I’ve spent the last three hours trying out different tags from here http://codex.wordpress.org/Template_Tags but things just got worse. Can anyone help me update the above code replacing the depreciated tags?

Thanks