Guillaume Perréal wrote:
> >
> > OR
> >
> > 2. create a view:
> > create view "station_fields" as select * from information where fieldname = 'station.type';
> >
> > then use:
> >
> > FOREIGN KEY ( "type") references "station_fields" ( code),
>
> I tried : it doesn't work. It seems that view rows don't have OID, which are used in foreign key. (I deduce that from
theerror messages I've got when I tried).
>
For gods sake they don't have. And I'm uncertain that it
should ever work.
The reason is that an FK constraint not only has to be
checked at INSERT/UPDATE time of the referencing table. It
must further ensure that later modifications to the
referenced table don't violate existing references. Now in
the case of a view that is a join over 3 tables, we setup a
multicolumn FK constraint over columns coming from different
base tables (or computed ones). How should a RESTRICT or ON
DELETE CASCADE work in that scenario?
Jan
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