Re: MV Keys

From: Marshall Spight <marshall.spight_at_gmail.com>
Date: 2 Mar 2006 10:59:19 -0800
Message-ID: <1141325959.909042.77180@j33g2000cwa.googlegroups.com>

Jon Heggland wrote:

> How do you define "repeating group" as opposed to "nested relation",
> then?

A repeating group is a set of attributes, all doing the same thing, but repeated to allow higher cardinality. Nested relation/RVA is a single atribute whose type is relation. An example of a repeating group is allowing up to three phone numbers for a customer by having three attributes, PhoneNumber1, PhoneNumber2, and PhoneNumber3. This approach has significant disadvantages.

(I was under the impression this usage was quite standardized; yes? No?)

> I assume "nested relation" and "relation-valued attribute" is the
> same thing.

Yes; that's how I'm using the terms. For some reason I prefer the "nested" term to the RVA term.

Marshall Received on Thu Mar 02 2006 - 12:59:19 CST