Re: Null in subquery returns no records

You will do yourself a favour to ignore Dawn. She is an idiot with an axe to grind who doesn't have a clue about effective data management.

Conflating NULL with the relational model is just one of her atrocious idiocies.

"Dan" <guntermannxxx_at_verizon.com> wrote in message news:FGbVb.244$4e3.185_at_nwrddc02.gnilink.net...
> What is the difference between a null, an "unknown value," and a null set?

Who knows really? NULL and 3-valued logic have so many problems they have reams written on them. Even if one considers them useful, and I do not, the inconsistencies in SQL render NULL meaningless.

God only knows what Dawn means when she talks about a null set. She might mean an empty set and she might not. My guess is she is so confused in her thinking she doesn't really know herself.

The products she recommends are simultaneously complex and feeble.

> Is a null set an empty set?
>
> If a null set means "a set with an unknown set of values", then what good
> does that do us from a logical perspective. Isn't that set as worthless
as
> an unknown value?
>
> What is returned from a null set if you don't use nulls?
>
> How does a null set help keep fidelity to two-value logic?
>
> Thanks,
>
> Dan
>
> "Dawn M. Wolthuis" <dwolt_at_tincat-group.com> wrote in message
> news:c02sjp$q4n$1_at_news.netins.net...
> > "Jonathan Leffler" <jleffler_at_earthlink.net> wrote in message
> > news:z%0Vb.17554$uM2.2847_at_newsread1.news.pas.earthlink.net...
> > > Mike MacSween wrote:
> > > > New testing rule for Mike - always test with null values.
> > >
> > > Alternative rule - always ensure the database stores no nulls!
> > >
> > > Not necessarily easy - but a good discipline.
> > >
> > <snip>
> > And perhaps the best option of all -- use one of the databases that
> employs
> > a two-valued logic, with NULLs treated as null sets -- much cleaner and
> > clearer. Examples are jBASE from www.jbase.com , Revelation from
> > www.revelation.com and the U2 databases (UniData and UniVerse) from
> > www.ibm.com (then do a search). You would not be alone as there are
over
> > 100,000 companies that use these products (could be a low estimate).
> >
> > I'm sure there are others as well that have avoided many of the SQL and
> > RDBMS complications. There is nothing holy nor scientifically more
> correct
> > about the RDBMS model than many other possibilities. If you have an
> > opportunity to free yourself of the notion that an RDBMS is required,
you
> > are likely to find a more productive environment elsewhere.
> >
> > Just thought I'd toss in my two cents even though most people who share
> this
> > opinion keep it quiet. --dawn
> >
> >
>
>
Received on Sat Feb 07 2004 - 23:15:58 CET