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From: allbery@NCoast.ORG (Brandon S. Allbery KB8JRR)
Newsgroups: comp.databases
Subject: Re: UNIFY RPT bug concatenating strings
Message-ID: <1990Nov23.192105.11710@NCoast.ORG>
Date: 23 Nov 90 19:21:05 GMT
References: <321@cti1.UUCP> <1p2ytsu@Unify.Com>
Reply-To: allbery@ncoast.ORG (Brandon S. Allbery KB8JRR)
Followup-To: comp.databases
Organization: North Coast Public Access *NIX, Cleveland, OH
Lines: 37

As quoted from <1p2ytsu@Unify.Com> by dxs@dbrus.Unify.Com (Dale R. Shaver):
+---------------
| In article <321@cti1.UUCP> kmeek@cti1.UUCP (Kevin Meek) writes:
| >When concatenating strings together if any of the fields in the input
| >are null then resulting output string is set to null as well.
| 
| It is true that RPT will set a value to NULL if one or more of the 
| elements is NULL.  This is true whether the values are strings, 
| numerics, amounts, etc.  However, this is the way in which the RPT
| product works; in other words, a feature.
+---------------

That maybe should be clarified:  according to the ANSI SQL standard, the only
operations on NULL values that do not return NULL are the "IS NULL" and "IS
NOT NULL" operations.  By the ANSI definition of NULL, concatenating a NULL
string with anything else returns the NULL string.

+---------------
| However, the bug here is that strings of length zero are being 
| interpreted as NULL when they should not be.  Given the input that 
| Kevin supplied:
+---------------

Interesting that you consider it a bug.  I had assumed it was there for the
multiple database support:  the last version of Informix-SQL I used, for
example, considered the empty string to be a NULL of type char(...).  (Not
that I consider that behavior correct, mind you; it's one reason I chose Unify
over Informix.)

++Brandon


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