Re: History of 1NF
Date: Thu, 13 Mar 2008 17:13:03 GMT
"paul c" <toledobysea_at_ac.ooyah> wrote in message
> David Cressey wrote:
> > "paul c" <toledobysea_at_ac.ooyah> wrote in message
> > news:1k%Bj.77466$w94.11329_at_pd7urf2no...
> >> David Cressey wrote:
> > I don't think normal form depends on introducing more attributes, but
> > decomposing tables. The columns introduced, namely foriegn keys, refer
> > attributes that are already there.
> "Attribute introduction" seems part and parcel of the Information
> Principle and normalization a consequence of that. If you started from
> scratch wanting to know what is the most popular combinations of parts
> then without physical tricks, such as graphics, some data needs to be
> added to.
> eg., customers A and B have both bought parts 1 and 2, customer C has
> bought part 1. It would be nice if a query answer didn't repeat
> customer numbers or pick one arbitrarily.
AFAIK, "Compose" does exactly that. I've never used compose, being stuck in the world of SQL. But there's an easy way around that, if it's important. Simply refrain from using the "*" wildcard in place of a list of columns. I know, I know, it's a pain, but it will do the trick.
Now, in order to prevent the customer number from appearing twice in the query response, all you have to do is not ask for it twice. Received on Thu Mar 13 2008 - 18:13:03 CET