Re: SQL - UNION statement

From: Jan Nowitzky <nowitzky_at_informatik.uni-jena.de>
Date: Tue, 08 Dec 1998 17:25:51 +0100
Message-ID: <366D530F.29EA47CB@informatik.uni-jena.de>

Matthias Gresz wrote:

> suisum_at_ecn.ab.ca schrieb:
> >
> > Hi all:
> >
> > Anyone know what the purpose of the following SQL statement? Why we need
> > UNION?
> > ...

Hi Matthias,

the difference is

(1) e.disb_no = '000' and
(2) e.disb_no != '000'.
The reason could be NULL-Values!

(1) supplies all disb_no which match the string '000'
(2) supplies all disb_no which doesent match these string. Especially it  means,
that tupels with disb_no = NULL will not be selected!

Regards,
Jan Received on Tue Dec 08 1998 - 10:25:51 CST