Message-ID: <1075.192.168.1.16.1042708067.squirrel@mainbox.archonet.com>
In-Reply-To: <20030116015932.10944.qmail@web80304.mail.yahoo.com>
References: <1522.192.168.1.16.1042651389.squirrel@mainbox.archonet.com>
	<20030116015932.10944.qmail@web80304.mail.yahoo.com>
Date: Thu, 16 Jan 2003 09:07:47 -0000 (GMT)
Subject: Re: RFC: A brief guide to nulls
From: dev@archonet.com
To: pgsql-sql@postgresql.org
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>
> --- 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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