SQL Sewer considers empty strings and nulls as different - it is very
annoying. The questioner must be from a SQL Sewer background.
"Niall Litchfield" <n-litchfield_at_audit-commission.gov.uk> wrote in message
news:3d639ab8$0$8507$ed9e5944_at_reading.news.pipex.net...
> "Wolfram Roesler" <wr_at_grp.de> wrote in message
> news:Xns927195BD69F7Awrgrpde_at_62.153.159.134...
> > "Vladimir M. Zakharychev" <bob_at_dpsp-yes.com> wrote in
> > news:ajvnht$rq8$1_at_babylon.agtel.net:
> >
> > > This is not a bug, this is design decision taken by Oracle long time
> > > ago and it is unlikely to change. You have to live with it - empty
> > > varchar2 in Oracle was NULL, is NULL and probably will be NULL for the
> > > life of Oracle database software.
> > >
> >
> > Is there any wisdom behind that design decision, or is it merely a
> > bug that had to be declared a feature for compatibility reasons?
> > I find it very counter-intuitive that, for example, ''='' and
> > ''!='X' are false.
>
> Maybe I'm just sheltered but I can't see any reason why anyone would
regard
> using the absence of any entry as signifying NULL a bug. What
representation
> would you use for unknown.
>
> As for counter-intuitive well I sort of agree. Thats because we've got so
> used to TRU/FALSE logic that tri-value logic throws us. If you think of
NULL
> as an unknown vale then you can rewrite your two comparisons as
>
> 1. Is this unknown value equal to this second unknown value? Clearly this
> can't be said to be either true or false but unknown.
> 2. Is this unknown value something other than 'X'? Again how can I
possibly
> say true or false to this.
>
> >
> > How do I join by an empty string, for instance? Consider:
>
> What you mean is how do I join two unknown values. This is a meaningless
> join.
>
> HTH
>
>
> --
> Niall Litchfield
> Oracle DBA
> Audit Commission UK
> *****************************************
> Please include version and platform
> and SQL where applicable
> It makes life easier and increases the
> likelihood of a good answer
>
> ******************************************
>
>
Received on Thu Aug 22 2002 - 12:48:17 CDT
