protected function valueLists( $rows, $columns ) {

        $lists = array();

        foreach ( $rows as $row ) {

            $values = array();

            foreach ( $columns as $column ) {

                $values[] = $this->quote( @$row[ $column ] );

            }

            $lists[] = "( " . implode( ", ", $values ) . " )";

        }

        return $lists;

    }