sad wrote:
On Friday 25 June 2004 09:37, Rosser Schwarz wrote:
On Fri, 25 Jun 2004 08:16:47 +0400, sad <[EMAIL PROTECTED]> 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
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