Re: Lots of Idiotic Silly Braces?
From: Bob Badour <bbadour_at_pei.sympatico.ca>
Date: Mon, 16 Jul 2007 19:58:56 -0300
Message-ID: <469bf80d$0$8848$9a566e8b_at_news.aliant.net>
>
> ...
>
>
> I guess I was using the word "table" pretty casually. I'm fairly sure
> Codd didn't mention it much, talking rather of "normalization", and
> maybe I shouldn't suggest to compare the two, eg., he said:
>
> "Normalization proceeds as follows. Starting with the relation
> at the top of the tree, take its primary key and expand
> each of the immediately subordinate relations by
> inserting this primary key domain or domain combination.
> The primary key of each expanded relation consists of the
> primary key before expansion augmented by the primary
> key copied down from the parent relation. Now, strike out
> from the parent relation all nonsimple domains, remove the
> top node of the tree, and repeat the same sequence of
> operations on each remaining subtree."
>
> If I follow this literally, I suppose the fact that I can't "strike out
> ... all nonsimple domains", means that I am left with what I started
> with, namely a relation, you are saying that the table and relation in
> this case are one and the same, and you might say I am grasping at
> graphical representation that is an impossible over-simplification!
Date: Mon, 16 Jul 2007 19:58:56 -0300
Message-ID: <469bf80d$0$8848$9a566e8b_at_news.aliant.net>
paul c wrote:
>> paul c wrote:
>
> ...
>
>>> The predicate somebody intends by this grouping could be "Shipment S >>> included the set of parts {P}". If we then ask "what combinations of >>> parts have been shipped?", a knee-jerk reation might be to project >>> away the S attribute: >>> >>> {P}: >>> {3,4} >>> {3} >> >> >> >> This represents it as one table. >> ...
>
> I guess I was using the word "table" pretty casually. I'm fairly sure
> Codd didn't mention it much, talking rather of "normalization", and
> maybe I shouldn't suggest to compare the two, eg., he said:
>
> "Normalization proceeds as follows. Starting with the relation
> at the top of the tree, take its primary key and expand
> each of the immediately subordinate relations by
> inserting this primary key domain or domain combination.
> The primary key of each expanded relation consists of the
> primary key before expansion augmented by the primary
> key copied down from the parent relation. Now, strike out
> from the parent relation all nonsimple domains, remove the
> top node of the tree, and repeat the same sequence of
> operations on each remaining subtree."
>
> If I follow this literally, I suppose the fact that I can't "strike out
> ... all nonsimple domains", means that I am left with what I started
> with, namely a relation, you are saying that the table and relation in
> this case are one and the same, and you might say I am grasping at
> graphical representation that is an impossible over-simplification!
Because the primary key is {P}, if you follow the instructions literally, you will normalize the relation to:
{P} P
==== ----
{3,4} 3
{3,4} 4
{3} 3
I do not believe his instructions anticipated a relation valued primary key. Received on Tue Jul 17 2007 - 00:58:56 CEST