Re: 1NF (Marshall)

On Jan 20, 6:59 am, "JOG" <j..._at_cs.nott.ac.uk> wrote:
> *bump*

Ha! The canoncal term is "ping" from the ICMP protocol.

But as to the actual question...

I would say that my understanding has moved somewhat, but not a lot. I still don't feel like 1NF is on anywhere near the firm foundation that, say, BCNF has. I've never heard a definition of "atomic value" that I find satisfactory. However I am finally convinced I know what "flat" means.

A guideline is that we wouldn't want to use a nested relation for something that we need to address individually. So even if invoices are completely contained within customers, we probably don't use a nested relation because we want to discuss invoices by themselves. Invoice line items, not so much. Antsther thing to look at is "on delete cascade" as a guideline that nesting might be appropriate.

It does seem to me, though, that despite any relaxing of 1NF, we can get ourselves in to trouble with too much nesting. However the reverse isn't true; there is no trouble associated with unnesting. At worst you are talking inconvenience.

Marshall Received on Sat Jan 20 2007 - 19:56:49 CET