You rarely ever need a custom SQL query, use the tools WordPress has to offer:
$query = new WP_Query(
array(
'posts_per_page' => -1,
'post_parent' => $post->ID,
'post_type' => 'page',
'orderby' => 'menu_order post_title',
'order' => 'ASC',
)
);
if ( $query->have_posts() ) : ?>
<?php while ( $query->have_posts() ) : $query->the_post() ?>
<div id="page-<?php the_ID() ?>">
<?php the_content() // Use any template tags as you would normally ?>
</div>
<?php endwhile ?>
<?php wp_reset_postdata() // Restore the current page ?>
<?php endif ?>