"SELECT $group FROM grouptable WHERE $group=DEFAULT( $group ) "
Or I think better:
"SELECT DEFAULT( $group ) FROM grouptable LIMIT 1 "
Update - correction
As @Jeff Caron pointed, the above will only work if there is at least 1 row in
grouptable. If you want the result even if the grouptable has no rows, you can use this:
"SELECT DEFAULT( $group )
FROM (SELECT 1) AS dummy
LEFT JOIN grouptable
LIMIT 1 ;"