Re: Base Normal Form
Date: Tue, 12 Jul 2005 09:19:36 -0700
Message-ID: <bsq7d1pbpoabrugf2bep07tg56cl54k6k7_at_4ax.com>
On 12 Jul 2005 02:57:08 -0700, "dawn" <dawnwolthuis_at_gmail.com> wrote:
[snip]
>It is easy enough to model a database relation with a set theory
Be careful about that amusement. Sometimes, it is because the
other people know more about the situation than you do. Surely, you
>relation, so this is not a problem, but when db relational theorists
>get all preachy on this unordered point, it amuses me.
[snip]
>So, remind me, what precisely is the problem with ordering the
>attributes in relations? It results in ... because ... ???
If you say that the ordering is significant, then (a,b,c) and (a,c,b)
are different. If you go purely by the name, they are the same. (I have omitted the types for simplicity. Assume that they are the same.)
This does not look like much, but consider a join. Now, you have to define which order the columns are in the join. Make sure you do it right, or you could end up with A join B and B join A resulting in different orderings.
[snip]
Gene Wirchenko Received on Tue Jul 12 2005 - 18:19:36 CEST