--- In firebird-support@yahoogroups.com, "Martijn Tonies"
<m.tonies@u...> wrote:

> Hi,
>
> > I came across this "Special" case. It seems that Firebird enforces
> > not null in the primary key when you create the table. (Makes 100%
> > sense) But sadly, it doesn't enforce the user from altering the
> > field. I was able to do an ALTER Table and remove the not null from a
> > primary composite key.
>
> No, you weren't. At least not via a standard ALTER statement,
> 'cause the NULL/NOT NULL attribute cannot be changed this
> way.

I went back and doubled check what I did. Your right, It wasn't an
Alter sql. I used IB Expert, and noticed that IB Expert updates the
relation table directly (update RDB$RELATION_FIELDS). Maybe I should
send a message to them about this. Since this can cause some issues.