<?php
// Look for a direct sidebar to this page
$querystr = "
	SELECT *
	FROM $wpdb->posts
	WHERE post_title = 'Sidebar'
	AND post_parent = $post->ID
	AND post_status = 'publish'
	AND post_type = 'page'
	ORDER BY post_date DESC
";
$direct_sidebar = $wpdb->get_results($querystr, OBJECT);

if($direct_sidebar) : // found a direct sidebar, set up postdata and display it
	global $post;
	foreach($direct_sidebar as $post) :
		setup_postdata($post);
		echo '<div class="sidebar">';
			the_content(); // display user's sidebar content
		echo '</div>';
	endforeach;
else : // no direct sidebar, check for a parent page sidebar
	$ancestors=get_post_ancestors($post->ID);
	$root=count($ancestors)-1;
	$parent = $ancestors[$root];

	$querystr = "
		SELECT *
		FROM $wpdb->posts
		WHERE post_title = 'Sidebar'
		AND post_parent = $parent
		AND post_status = 'publish'
		AND post_type = 'page'
		ORDER BY post_date DESC
	";
	$parent_sidebar = $wpdb->get_results($querystr, OBJECT);
	if($parent_sidebar) :
		global $post;
		foreach($parent_sidebar as $post) :
			setup_postdata($post);
			echo '<div class="sidebar">';
				the_content();
			echo '</div>';
		endforeach;
	endif;
endif;

?>