Re: 3vl 2vl and NULL

From: David Cressey <dcressey_at_verizon.net>
Date: Thu, 15 Dec 2005 22:46:19 GMT
Message-ID: <%mmof.4827$Kk7.477_at_trndny05>


"Hugo Kornelis" <hugo_at_pe_NO_rFact.in_SPAM_fo> wrote in message news:nno3q1ljlrs95ughnt3jf84jvqolts98bt_at_4ax.com...
> But this case is different. The data was missing. And instead of
> treating this data as being missing, the DB simply assumed some value
> (apparently a zero in this case) and reported on it as if that was the
> value I entered on the form yesterday. This would be the "nothing in
> garbage out" principle.
>

I think at this stage it's worth distinguishing between "not asserted to be older than Aunt Marge" and "asserted to be not older than Aunt Marge".

They aren't the same thing. This may be what you are already saying Hugo, but in different words.

> >
> >I have not done any tests with this, but there is something about
> >seeing the incorrect data on a report that helps with data cleansing,
> >with the downside that someone might believe that Uncle Vernon is
> >younger than Aunt Marge and this could cause some problem. There are
> >pros and cons to each, but it really is far easier to work with a 2VL.
> >I doubt anyone who has worked extensively with both would say
> >otherwise.
>

> Would ten years of programming applications in various thrid-generation
> languages qualify as "worked extensively" with 2VL?
>
> Would nine years of developing database applications in SQL databases
> qualify as "worked extensively" with 3VL?
>
> If the answer to both these questions is yes, you can now say "Hi" to
> someone who has worked extensively with both and who would definitely
> say otherwise. ;-)
>

Me too, as far as experience goes. But I prefer to deal with a 2vl, and treat "unknown" as an unusual case. I've never had trouble thinking in 2VL and expressing things in SQL. But then, I tend to filter out NULLS before they can cause me any grief.

I don't filter them out at write time (except in a DW). I fileter them out at select time.

> Best, Hugo
> --
>
> (Remove _NO_ and _SPAM_ to get my e-mail address)
Received on Thu Dec 15 2005 - 23:46:19 CET

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