Re: The MySQL/PHP pair

"Paul" <paul_at_test.com> wrote in message news:418bcfd1$0$33598$ed2619ec_at_ptn-nntp-reader02.plus.net...
> Dawn M. Wolthuis wrote:
> > I know I have some reading to do re 2nd order logic so that I really
> > understand just where we move from 1st to 2nd order logic being required
and
> > just where 2nd order logic is problematic when querying data.
> >
> > What is the problem if I want to persist the proposition:
> >
> > Person
> > Bob Smith has e-mail addresses of bob_at_aol.com and bobsmith_at_msn.com
>
> Well, want you really want to do (or at least what the relational model
> does) is collect together all propositions that fit the same "template"
> and store them together.
>
> If you do this as:
>
> Person P has email addresses of E1 and E2
>
> then you are restricted to two email addresses per person.
> What you are really saying you want to do is collect together:
>
> Bob Smith has e-mail addresses of bob_at_aol.com and bobsmith_at_msn.com
> Jane Doe has an e-mail address of jdoe_at_aol.com
> Bill Bloggs has e-mail addresses of bill_at_yahoo.com, bill_at_hotmail.com
> and bill_at_aol.com
>
> But the predicate for this would be something like:
>
> Person P has email addresses of E1, E2, E3, ...

or

Person P has the following list of e-mail addresses: L

and it is only if there is a question that requires a function to look into the values of L would we then apply that function so that we could ask:

who has e-mail addresses at aol.com?

> and it's this unknown number of parameters that is the problem - a first
> order predicate has to have a fixed number of parameters.

Given that we can use SQL to GROUP data and if we can also UNGROUP data, then where does the 2nd order predicate logic come in and why is it a problem? Again, I really am ignorant on where we hit a wall with first order predicate logic and what the problem is with introducing additional logic to handle nesting and unnested as needed. Thanks for your help. --dawn

> Paul.
Received on Fri Nov 05 2004 - 20:58:40 CET