Uhm, sorry for the noise, but the problem solved itself,
kind of ...
I wasn't aware that a foreign key actually _can_ be null.
The docs weren't very specific about that. Thinking that
a foreign key must contain a valid reference to another
table (after all, that's what a foreign key is for), I
implied that it cannot be null -- which was wrong.
Thanks for listening anyway. :-)
Regards
Oliver
--
Oliver Fromme, secnetix GmbH & Co KG, Oettingenstr. 2, 80538 München
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