$sql = "SELECT name,slug,$wpdb->terms.term_id as ID,parent FROM $wpdb->terms ".
       "LEFT JOIN $wpdb->term_taxonomy ON ($wpdb->terms.term_id = $wpdb->term_taxonomy.term_id) ".
       "WHERE parent=5 AND taxonomy='category' ORDER BY name ASC";
$categoryList = $wpdb->get_results($sql);

echo categoryPrint($categoryList);



function categoryPrint($results, $multiple = "", $subcat_level = 0){
  global $wpdb;
  if(!$results){return;}
  foreach($results as $a_cat){
    if($multiple){
      categoryPrintSelectItem($a_cat, $subcat_level);
    }
    else{
      categoryPrintItem($a_cat, $subcat_level);
    }
    $sql = "SELECT name,slug,$wpdb->terms.term_id as ID,parent FROM $wpdb->terms ".
           "LEFT JOIN $wpdb->term_taxonomy ON ($wpdb->terms.term_id = $wpdb->term_taxonomy.term_id) ".
           "WHERE parent=$a_cat->ID AND taxonomy='category' ORDER BY name ASC";
    $sub_cats = $wpdb->get_results($sql); 
    categoryPrint($sub_cats, $multiple, $subcat_level + 1);
  }
}
function categoryPrintSelectItem($a_cat, $subcat_level){
  for($i = 0; $i < $subcat_level; $i++){
    echo "…";
  }
  echo $a_cat->name."</option>\n";
}
function categoryPrintItem($a_cat, $subcat_level){
  for($i = 0; $i < $subcat_level; $i++){
    echo "{$a_cat->name}<br>";
  }
  if($subcat_level < 1){
    echo "<b><h3>{$a_cat->name}</h3></b><br>";
  }
}

WHERE parent=5