Re: atomic

From: paul c <>
Date: Fri, 02 Nov 2007 14:56:30 GMT
Message-ID: <yUGWi.169136$th2.69454_at_pd7urf3no>

Jon Heggland wrote:

>> I'm wondering are there applications where RVA values that are "empty"
>> make sense or are such values just a curious by-product of RVA's?

> Consider the standard example of relvars and keys. Though of course,
> empty RVA values are in some sense a by-product of RVAs... :)

The relvars and keys example might be a little more interesting than mine. I'd say this is because D&D emphasize that an empty header can be a key. But if it is, then there would be only one tuple for a given relation that has an empty RVA, no other tuples for that RVA. I suppose if RVA's weren't allowed, a dbms that didn't support RVA's would have to   presume the empty header as a key when no other set of attributes was specified. Received on Fri Nov 02 2007 - 15:56:30 CET

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