Re: foundations of relational theory? - some references for the truly starving

In article <1b0b566c.0311092212.57b13af0_at_posting.google.com>, Mike Preece <michael_at_preece.net> writes
>> It doesn't. Pick is not relational. I was just showing a mapping between
>> the relational model and Pick's physical model, thereby exposing a weakness
>> in the physical model. To preserve "PK persistence" as you call it, one
>> would need to actually have a PK for the MV columns. This would be
>> problematic, since it's really a collection of MV columns synchronized
>> together that form a nested relation, and Pick itself doesn't know about the
>> multi-column association; it's up to the application to maintain this.
>>
>
>Isn't the PK preserved anyway? The position of a multivalue is
>inherent - if the datum changes its position so does it's PK change.

And aren't PKs optional in relational theory, anyway?

Cheers,
Wol

-- 
Anthony W. Youngman - wol at thewolery dot demon dot co dot uk
Witches are curious by definition and inquisitive by nature. She moved in. "Let 
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Maskerade : (c) 1995 Terry Pratchett