Message-ID: <20030116015932.10944.qmail@web80304.mail.yahoo.com>
Date: Wed, 15 Jan 2003 17:59:32 -0800 (PST)
From: Ludwig Lim <lud_nowhere_man@yahoo.com>
Subject: Re: RFC: A brief guide to nulls
To: dev@archonet.com
Cc: PostgreSQL Mailing List <pgsql-sql@postgresql.org>
In-Reply-To: <1522.192.168.1.16.1042651389.squirrel@mainbox.archonet.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii


--- dev@archonet.com wrote:
> There have been a few posts recently where people
> have had problems with
> nulls. Anyone got comments on the below before I
> submit it to techdocs?
> 
> TIA
> 
> - Richard Huxton
> 
> A Brief Guide to NULLs
> ======================
> 
> What is a null?
> ===============
> A null is *not* an empty string.
> A null is *not* a value.
> A null is *not* a "special" value.
> A null is the absence of a value.
> 
> 
> What do nulls mean?
> ===================
> Well, they *should* mean one of two things:
> 1. There is no applicable value
> 2. There is a value but it is unknown

  Good job!, it sure helps people who don't much
background on formal database theory.

  What about adding this to the section "What does
nulls mean"
 --> 3) No value has yet been assigned to that
particular attribute (field).

  
  I think it would also be nice if you can add a
section on functions that deals with NULL such as
nullif() and coalesce(). These functions help users
interpret NULL values.


best regards,

ludwig


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