您可以尝试以下操作：

$args = array (
    \'post_type\'              => \'books\',
    \'name\'                   => \'\',
    \'post_status\'            => array(\'publish, draft\'),
    \'posts_per_page\'         => -1,
    \'meta_query\'             => array(
        array(
            \'key\'       => \'book_isbn_id\',
            \'value\'     => \'dummy\',
            \'compare\'   => \'NOT EXISTS\',
            \'type\'      => \'NUMERIC\',
        ),
    ),
);

add_filter( \'posts_where\', \'custom_posts_where\' );
$query = new WP_Query( $args );
echo $query->request;

function custom_posts_where( $where )
{
    remove_filter( current_filter(), __FUNCTION__ );
    if( FALSE === strpos( $where, \'post_name\' ) )
    {
        $where .= sprintf( " AND %s.post_name = \'\' ", $GLOBALS[\'wpdb\']->posts );
    }
    return $where;
}