Re: Dreaming About Redesigning SQL

"Marshall Spight" <mspight_at_dnai.com> wrote in message news:h%Qob.56961$mZ5.338904_at_attbi_s54...
> "Mike Preece" <michael_at_preece.net> wrote in message
news:1b0b566c.0310312141.67b3f186_at_posting.google.com...
> > In the relational model, as in the Pick model, if everyone had just
> > one unique phone number (or none at all), the phone number could be
> > considered to be an attribute of the person in exactly the same way
> > that their name or date of birth could be.
>
> Yes.
>
>
> > If it becomes necessary to record more than one phone number against a
> > person, does the relational model dictate that the logical schema must
> > change?
>
> Yes. Doesn't the Pick model as well?

Yes and no. Pick will never prevent a user from entering multiple values where the designer anticipates a single value. In this sense, one does not need to tell Pick anything different to accept multiple values. However, when the user enters multiple values, the user will implicitly change the meaning of all existing queries that anticipate a single value, and in this sense the Pick logical data model requires the logic to change as well.

> Isn't the size constraint on the
> number of phone numbers part of the schema?

Not in Pick. It lacks integrity.

> > I don't know the correct terminology, but would the list of
> > phone numbers for a person have to be held separately in its own table
> > and "referred to"?
>
> This is standard practice, but I'm not sure if "have to" is the right way
> to say it.
>
>
> > This doesn't have to happen in Pick. An attribute can be multivalued.
>
> Are you considering an attribute changing from single-valued to
multivalued
> as NOT being a schema change? Or does Pick not have a way to distinguish
> between the two cases?

The way Pick will interpret queries changes when the data becomes multivalued, but Pick makes no particular distinction in the schema. For some reason, Pickies think not knowing how the product will interpret the data is an advantage. As I have repeated many times, these individuals are ignorant and stupid.

> > Do you agree that a list of a person's phone numbers can and should be
> > considered an attribute of the person - just as a single number is -
> > provided an acceptable means exists to access all "rows" containing a
> > given phone number?
>
> Roughly speaking, this works for me, but I think it hinges on
> the definition of the word "attribute."
>
>
> Marshall
>
>
Received on Sun Nov 02 2003 - 00:51:53 CET