Average of Custom Field linked to Category

Here is sample code showing how to do this:

$category_name = 'CAT01';
$meta_key = 'Test01';
$sql = "
select avg(pm.meta_value)
from $wpdb->postmeta pm
join $wpdb->posts p on p.ID = pm.post_id
where pm.meta_key = '$meta_key'
and p.ID in (
   select ID from $wpdb->posts p2
   join $wpdb->term_relationships tr on p2.ID = tr.object_id
   join $wpdb->term_taxonomy tt on
     (tt.term_taxonomy_id = tr.term_taxonomy_id AND tt.taxonomy = 'category')
   join $wpdb->terms t on (t.term_id = tt.term_id and t.name = '$category_name')
   )
";
$avg = $wpdb->get_var($sql);
echo "<p>AVERAGE $meta_key = $avg </p>";