Re: Query plan for NOT IN

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От Guy Rouillier
Тема Re: Query plan for NOT IN
Дата
Msg-id 4ACA4A69.3010507@burntmail.com
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Ответ на Re: Query plan for NOT IN  (Grzegorz Jaśkiewicz <gryzman@gmail.com>)
Ответы Re: Query plan for NOT IN  (Grzegorz Jaśkiewicz <gryzman@gmail.com>)
Список pgsql-performance
Grzegorz Jaśkiewicz wrote:
>
> well, as a rule of thumb - unless you can't think of a default value of
> column - don't use nulls. So using nulls as default 'idunno' - is a bad
> practice, but everybody's opinion on that differ.

I don't understand this point of view.  The concept of null was
introduced into the SQL vernacular by Codd and Date expressly to
represent unknown values.

--
Guy Rouillier

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