Re: Question on Structuring Product Attributes

On Mon, 11 Feb 2013 02:51:46 -0800 (PST) Derek Asirvadem <derek.asirvadem_at_gmail.com> wrote:

>
> On Monday, 11 February 2013 11:38:54 UTC+11, James K. Lowden wrote:
> > On Sat, 9 Feb 2013 16:34:51 -0800 (PST) derek.a..._at_gmail.com wrote:
> >
> > Could you please tell me which 3VL supports your contention that
> > NULL = NULL?

> Where, in [quote omitted], does the implicit or explicit statement
> lie, that 3VL or "a" 3VL, contends that NULL = NULL ?
...
> To be clear:
> ? Sybase ANSI_NULL_BEHAVIOUR = OFF (where NULL = NULL)
> is 2VL.

Um, no. A logic with 3 values can't be a 2VL.

This is c.d.t.; we're supposed to be able to refer here to the theory of databases. I showed you a truth table and asked which 3VL you were referring to. If you're going to contend that 2 values are 3, I'm going to stand well clear.

> > > SQL is [the] data sublanguage defined in the RM; it is the
> > > servant of the RM, not the other way around.
> >
> > If only.
>
> Hah! I love it!
>
> You young people think that history began when you were born,

I was born ... when?

> > AFAIK the word "relational" doesn't appear in the SQL
> > standard unless to explicitly deny fealty to it.
>
> So what ? It is a standard.

Yes, it's a standard defined explicitly in terms of itself, not in terms of RM. Your claim that, "SQL is [the] data sublanguage defined in the RM" is thus denied.

> Standards generally do not include history; the books or articles do
> that (or the memories of old soldiers like me), and the books are
> sadly wanting.

Standards generally do not rest on much of any theory, let alone something as robust as RM. It would have been nice if a standard query language had evolved that implemented relational operations per se. Instead we're living with a 1970s-era 4GL, a pushme-pullyou brute. IBM imagined it would be used by end-users, who at long last would write their own !_at_#$% reports. They didn't, and now programmers, lacking any proper mathematical expression, are required to squoosh their queries through the opaque mess that is SQL.

> I strongly suggest you throw out any book that purports to be about
> the RM, that is not written by Dr E F Codd, and read only the RM and
> related papers.

It's good advice. A little late, and more than a little presumptuous, but good advice, no doubt. I would only add that Codd is easier to understand and appreciate with some prior knowledge of first order predicate logic.

> There is one particularly odious idiot who proposes an anachronism:
> remove the data sublanguage and replace it with an, um, full
> language.

I guess you are referring to Tutorial D? Why the circumlocution?

--jkl Received on Mon Feb 11 2013 - 16:19:34 CET