Re: I have read tons of theory...but still...one question

From: Marshall Spight <mspight_at_dnai.com>
Date: Sat, 16 Oct 2004 23:22:57 GMT
Message-ID: <l3icd.193833$wV.79092_at_attbi_s54>


"Dawn M. Wolthuis" <dwolt_at_tincat-group.comREMOVE> wrote in message news:cks57p$kd9$1_at_news.netins.net...
>
> It was in this thread and I think I said it, but I meant it to be the
> primary key of this child-table, with the person's identifier also obviously
> part of the key if this sub-table is not embedded in the parent table.

So let me ask how this "embedded sub-table" works, because I'm intrigued by NFNF but haven't had an opportunity to work with such a system.

Does the embedded sub-table (EST) have its own key? Is it unique across the entire relation-valued attribute, or is in only unique for the row?

For example, let's say I have a relation of (l=letter, set-of-(i=int, s=string)). l is the key of the outer table; i is the key of the inner table. (Or is it (l,i)?)

Is this a legal table:
a,{(1,"hello")}
b,{(1, "world"),(2,"foo")}

Two rows have a value 1 for some i.

It seems both right and wrong either way. This is pretty much my only (current) point of confusion about RVAs.

> I tried to answer from a relational perspective, but I've been warped
> by having something easier to work with at hand.

Heh. You're starting to get snarky on that point. :-)

Marshall Received on Sun Oct 17 2004 - 01:22:57 CEST

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