Re: A question for Mr. Celko

Jan Hidders <jan.hidders_at_REMOVETHIS.pandora.be> wrote in message news:<pan.2004.07.19.22.47.17.805097_at_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.
>
> Just extracting them is not the problem.
>

I am clearly not understanding you, because it sounds to me like these two statements are contradicting each other. What about UNNESTing a relation-valued attribute is different from extraction? Why does that introduce any problems? I'm really trying to understand this because it would certainly change my view of non-scalar-valued attributes if it can be shown that they cause some major problem in the logical model. So far, I have not seen any compelling arguments that they do.

Regards,
Bryn Received on Tue Jul 20 2004 - 06:42:34 CEST