Re: Null comparisons (was Re: checksum)

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От Greg Stark
Тема Re: Null comparisons (was Re: checksum)
Дата
Msg-id 87y8iv7ncd.fsf@stark.xeocode.com
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Ответ на Null comparisons (was Re: checksum)  (Stephan Szabo <sszabo@megazone.bigpanda.com>)
Ответы Re: Null comparisons (was Re: checksum)  ("Dean Gibson (DB Administrator)" <postgresql3@ultimeth.com>)
Список pgsql-general
Stephan Szabo <sszabo@megazone.bigpanda.com> writes:

> > On Sun, 26 Sep 2004 20:16:52 +0200, David Helgason <david@uti.is> wrote:
>
> > > On a similar note, I've found myself wanting an extended '=' operator
> > > meaning
> > >         (a = b or (a is null and b is null))
>
> The original does appear to be equivalent to "not(a is distinct from b)",
> although I'm not sure that's necessarily easier to use than the above.

I often do things like "coalesce(a,0) = coalesce(b,0)".
(Or whatever value you know won't appear)

Though for pretty small values of "often". It always makes me think twice
about my data model when I find myself doing this. But there are definitely
still cases where it's useful and as clean as anything else I could think of.

--
greg

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