Message-ID: <40DBEEB0.40203@archonet.com>
Date: Fri, 25 Jun 2004 10:21:52 +0100
From: Richard Huxton <dev@archonet.com>
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To: sad <sad@bankir.ru>
Cc: Rosser Schwarz <rosser.schwarz@gmail.com>,
	pgsql-sql@postgresql.org
Subject: Re: feature request ?
References: <200406250816.47781.sad@bankir.ru>
	<200406251020.41387.sad@bankir.ru> <40DBE35A.70104@archonet.com>
	<200406251154.05331.sad@bankir.ru>
In-Reply-To: <200406251154.05331.sad@bankir.ru>
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sad wrote:
>>sad wrote:
>>
>>>On Friday 25 June 2004 09:37, Rosser Schwarz wrote:
>>>
>>>>On Fri, 25 Jun 2004 08:16:47 +0400, sad <sad@bankir.ru> wrote:
>>>>
>>>>>>Very simply, a boolean may have to values: true or false.  It's also
>>>>>>possible that it's not been set to anything (NULL).
>>>>>
>>>>>really ?
>>>>>what about   (13 < NULL)::BOOL
>>>>
>>>>Per the semantics of NULL, 13 is neither greater than nor less than
>>>>NULL.  NULL is the *unknown* value; it's impossible to meaningfully
>>>>compare it to anything else. Try (NULL = NULL)::boolean. It's NULL,
>>>>also.
>>>
>>>READ THE THREAD BEFORE ANSWER
>>
>>WHAT MAKES YOU THINK HE HASN'T?
> 
> 
> I had answered to the proposal to PROHIBIT NULL VALUES 

Umm - what proposal?

Geoffrey wrote:
 > Very simply, a boolean may have to values: true or false.  It's also
 > possible that it's not been set to anything (NULL).

You replied:
 > really ?
 > what about   (13 < NULL)::BOOL

Which is an example where a boolean variable is undefined/not set/null.

In reply to you, Rosser Schwarz wrote:
 > Per the semantics of NULL, 13 is neither greater than nor less than
 > NULL.  NULL is the *unknown* value; it's impossible to meaningfully
 > compare it to anything else. Try (NULL = NULL)::boolean. It's NULL,
 > also.
 >
 > Since no value, including NULL, is in any way definitively comparable
 > to NULL -- the unknown value -- comparing to NULL results in ...
 > unknown.
 >
 > Otherwise known as NULL.

None of which suggests prohibiting nulls.

> 
>>The key point of argument, and where the problem is with your (13 <
>>NULL)::BOOL point is this:
> 
> 
> IT IS NOT MY PROBLEM !!! it is an EXAMPLE WHY WE CAN NOT PROHIBIT NULLS !!!

Umm - who is suggesting prohibiting nulls? I've re-read the entire 
thread and can't find any such suggestion. Is this one of those 
occasions where the different dialects of English are causing confusion?

-- 
   Richard Huxton
   Archonet Ltd