On Wednesday 21 July 2004 14:58, Markus Bertheau wrote:
> > 4) Replication: to identify an object of ANY type (record of any table
> > regardless to datamodel), to store lists of deleted or modified objects
> > (regardless to datamodel)
>
> That sounds like a datamodel on data that belongs to another data model,
that's right, these surr. keys actually belong to a metadata model,
but it is also useful to references of a data model. and they are used this
way.
> > 5) Making a primary key: if there is no real key at all.
>
> When there's no key at all, there can't be a surrogate key, as I
> understand it. In such cases a generated unique number comes in handy,
> and it's a real primary key and no surrogate key.
...right. in case (5) we construct another datamodel indeed. with an
artifichial real key :-)
P.S. r u from Russia ?