Hi Alexander, Carsten,

> > But why can i insert a foreign key for this column without any
> > exception.
> > The field id_mitarbeiter is primary key for t_mitarbeiter and there
> is
> > no null value allowed.
>
> Carsten, I can't recall exactly when (what was FB build number, but
> definetely before release of FB1) this feature was included, but FK
> can contain not only values which match PK of referenced table but
> nulls too. Perhaps Martijn can remember more exactly, he was among
> those who wanted this feature. Personally I prefer old, more
> restrictive behaviour, but I was among minority and feature was
> approved by developers and implemented.

Actually, I think I've wanted a feature related to UNIQUE constraints
with NULLs ... And I don't think it was included in Fb1. As for the FK,
as far as I know, they will still only allow values as to be found in the
constraint (unique/pk) they are referring to.


With regards,

Martijn Tonies
InterBase Workbench - the developer tool for InterBase & Firebird
Firebird Workbench - the developer tool for Firebird
Upscene Productions
http://www.upscene.com

"This is an object-oriented system.
If we change anything, the users object."