Re: A question for Mr. Celko

From: Jan Hidders <jan.hidders_at_REMOVETHIS.pandora.be>
Date: Mon, 19 Jul 2004 22:46:34 GMT
Message-Id: <pan.2004.07.19.22.47.17.805097@REMOVETHIS.pandora.be>

On Mon, 19 Jul 2004 11:38:57 -0700, John Jacob wrote:

>> No no, that's not the problem, or at least not what I think is the
>> problem. Date allows the NEST and UNNEST operations from the nested
>> relational algebra. (He calls them GROUP and UNGROUP for some reason.)
>> That means that you no longer consider them atomic because they allow you
>> to split a nested relation into its constituent parts.

>
> Does allowing this expression: StringVar[5] make the value in
> StringVar non-atomic?

No.

> Similarly, a
> relation-value is still a relation-value whether or not it is
> contained within a relation-value itself.

Correct.

> I don't see how this changes
> the definition of atomic.

It doesn't.

> Indeed, if you allowed relation-value
> attributes, but were not allowed to extract them from the relation,
> what use would they be?

Just extracting them is not the problem.

Jan Hidders

Received on Mon Jul 19 2004 - 17:46:34 CDT