Patrick,
> I tried recently (pgsql 7.1.2) to establish the oid of one table as
> foreign key
> in another.
> To no avail : there was no uniqueness constraint on that column
> Naturally, it seems impossible to add a uniqueness constraint to such
> a system
> column.
> As far as i know, the oid is by nature unique, excepting for the case
> of
> wrapping of their sequence.
> Is there any workaround ?
Yes. Don't use the OID as your key.
While it would be entirely possible for you add a unique constraint to
the OID column, you do not want to use it as your key for a number of
reasons previously discussed on this list (OID wraparound, problems with
backup and restore, etc.).
Instead, re-create the table with a new ID column of type SERIAL with a
PRIMARY KEY constraint. This will automatically create an
auto-incrementing sequence of unique values perfect for attaching
foriegn keys.
-Josh
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