Re: BUG #6669: unique index w/ multiple columns and NULLs

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От Jeff Davis
Тема Re: BUG #6669: unique index w/ multiple columns and NULLs
Дата
Msg-id 1338845461.27297.21.camel@sussancws0025
обсуждение исходный текст
Ответ на Re: BUG #6669: unique index w/ multiple columns and NULLs  (Bruce Momjian <bruce@momjian.us>)
Ответы Re: BUG #6669: unique index w/ multiple columns and NULLs  (jo <jose.soares@sferacarta.com>)
Список pgsql-bugs
On Mon, 2012-06-04 at 11:56 -0400, Bruce Momjian wrote:
> I get your point about COUNT(*) really counting rows, not values, but
> why doesn't GROUP BY then skip nulls?

A while ago, I came to the conclusion that applying logic to extrapolate
the behavior of NULL is a bad idea:

http://thoughts.davisjeff.com/2009/08/02/what-is-the-deal-with-nulls/

Jose was not wrong about the inconsistency between UNIQUE and GROUP BY.
But the answer is that "we do it that way because the standard says so".
And that's a good reason.

Regards,
    Jeff Davis

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