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From:Paul DuBois Date:February 16 2003 8:22pm
Subject:Re: bk commit into 4.0 tree (1.1560) [ARRRRRRGGGGGGHHHHHHH!!!!!]
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At 21:24 +0200 2/16/03, Michael Widenius wrote:
>Hi!
>
>A very small update.
>
>>>>>>  "Sergei" == Sergei Golubchik <serg@stripped> writes:
>
>Sergei> Hi!
>>>  Sergei,
>>>
>>>  Thanks, although I'm still wondering about why the NULL-always-sorts-first
>>>  change was made for 4.0.2.  Wasn't that done for ANSI compliance?  Did
>>>  the ANSI spec change?
>
><cut>
>
>Sergei>   ANSI X3.135-1992 (Database Language SQL) in section 13.1, General
>Sergei>   Rule 3)b), page 309, says "Whether a sort key value that is null is
>Sergei>   considered greater or less than a non-null value is implementation-
>Sergei>   defined, but all sort key values that are null shall either be
>Sergei>   considered greater than all non-null values or be 
>considered less than
>Sergei>   all non-null values."
>
>The problem is that the above doesn't spell out how NULL is affected
>by DESC.  As NULL can't be compared and are not ordered (by
>definition) it's not clear from the above (at least to me) what DESC
>is supposed to do.

It seems to have one of two possible meanings:

- NULL is less than non-null.  The implication is that NULL will sort
   first for ASC, and therefore last for DESC.
- NULL is greater than non-null. The implication is that NULL will sort
   last for ASC, and therefore first for DESC.

>
>Anyway, as Sergei said, the current (changed) behaviour is probably
>what ANSI SQL means and is most like the way most other database is
>handling DESC with NULL.  Sorry again for the confusion....

Okay.  Please don't change NULL sorting again for at least 10 years. :-)

>
>Regards,
>Monty

Thread
bk commit into 4.0 tree (1.1560)monty6 Feb
  • Re: bk commit into 4.0 tree (1.1560) [ARRRRRRGGGGGGHHHHHHH!!!!!]Paul DuBois7 Feb
    • Re: bk commit into 4.0 tree (1.1560) [ARRRRRRGGGGGGHHHHHHH!!!!!]Sergei Golubchik10 Feb
      • Re: bk commit into 4.0 tree (1.1560) [ARRRRRRGGGGGGHHHHHHH!!!!!]Paul DuBois10 Feb
        • Re: bk commit into 4.0 tree (1.1560) [ARRRRRRGGGGGGHHHHHHH!!!!!]Sergei Golubchik11 Feb
          • Re: bk commit into 4.0 tree (1.1560) [ARRRRRRGGGGGGHHHHHHH!!!!!]Michael Widenius16 Feb
            • Re: bk commit into 4.0 tree (1.1560) [ARRRRRRGGGGGGHHHHHHH!!!!!]Paul DuBois16 Feb
Re: bk commit into 4.0 tree (1.1560) [ARRRRRRGGGGGGHHHHHHH!!!!!]Peter Gulutzan11 Feb
Re: bk commit into 4.0 tree (1.1560)[ARRRRRRGGGGGGHHHHHHH!!!!!]Peter Gulutzan11 Feb
Re: bk commit into 4.0 tree (1.1560) [ARRRRRRGGGGGGHHHHHHH!!!!!]Peter Gulutzan17 Feb