[Zope] Problems with "Subselect" in SQL statment

[Florian Schuler]

Hello List,

I have a problem using ZSQL Methods. If I do something like this:

select * from person where id != (Select userid from projektmitglieder
where projektid='20');

Zope gives me an error ! 
Error Type: ProgrammingError
Error Value: ERROR: More than one tuple returned by a subselect used as
an expression. select * from person where id != (Select userid from
projektmitglieder where projektid='20');

But if I try this on the test chapter of my DB adapter is works and the
ZSQL Method also works well if I call it manually !!

Does someone knows a solution

Thanks in advance

Florian Schuler