Re: RFE: Column aliases in WHERE clauses

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От David Johnston
Тема Re: RFE: Column aliases in WHERE clauses
Дата
Msg-id 00f901cd972d$c6dae850$5490b8f0$@yahoo.com
обсуждение исходный текст
Ответ на Re: RFE: Column aliases in WHERE clauses  (Chris Angelico <rosuav@gmail.com>)
Список pgsql-general
>
> On Wed, Sep 19, 2012 at 11:15 PM, David Johnston <polobo@yahoo.com>
> wrote:
> > I could maybe see something like the following having some value:
> >
> > SELECT inverse
> > FROM data
> > WHERE x<>0 AND inverse > .5
> > MACRO inverse (1/x)
> >
>
> WITH macros AS (SELECT *,1/x AS inverse FROM data) SELECT inverse FROM
> macros WHERE x<>0 AND inverse > .5
>

In your example the "macro" has to either be attached directly to the FROM
or be used as part of a sub-select; it is not a text substitution macro at
all.  The pre-processor upon encountering a macro, would simply replace all
identifiers (at the same level in the query) with "(expression)".

David J.




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