Date: Fri, 02 Nov 2007 14:56:30 GMT
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