The query: SELECT foo.abc FROM (select abc from bar) foo; 

When parsing the query, gda_sql_parser_parse_string, mark the top node as UNKNOWN instead of a Select.

That is a valid query on sqlite3 and mysql, see:

sqlite> create table bar(abc varchar(10));
sqlite> insert into bar values('hi');
sqlite> SELECT foo.abc FROM (select abc from bar) foo;
hi


Seems like that syntax was not handled by the parser.y lemon file. So I have a patch for it: 
https://github.com/arthurnn/libgda/commit/0ba0e8f49f90304256e4fca637928d8cad55a1e0

I also sent the patch through the mailing list, but let me know if you need more info.

Thanks