> and all the tables in my database has a column called "ID" wich is the PK. As a
> matter of fact I didn't mean to have that domain as nullable. It was my mistake
> I think... But my question is: It's normal that FB didn't complain about having
> a PK on a nullable column?

I've just tested and it seems that FB silently added not null flag to
field declared as primary key.
If you create table with nullable column and then try to alter it
adding primary key, FB will complain.

SY, SD.