code: protected function buildOrderBy()/*# : array */
      {
          $result = [];
          foreach ($this->clause_orderby as $ord) {
              $result[] = $ord[0] ? $ord[1] :
                  ($this->quote($ord[1]) . ' ' . $ord[2]);
          }
          return $result;
      }
docs: Build ORDER BY
  
  @return array
  @access protected