Re: dynamic crosstab

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От David Fetter
Тема Re: dynamic crosstab
Дата
Msg-id 20080219181959.GD23041@fetter.org
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Ответ на Re: dynamic crosstab  (Alvaro Herrera <alvherre@commandprompt.com>)
Ответы Re: dynamic crosstab
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On Tue, Feb 19, 2008 at 11:56:08AM -0300, Alvaro Herrera wrote:
> Joe Conway wrote:
> > Erik Jones wrote:
> >> See how postgres handles filling the NULLs for you?  What you'd
> >> really  want to do with this would be to define some functions
> >> for setting and  getting a person's answers to a given question
> >> or set of questions so  that you could implement some kind of
> >> data integrity with regards to  question ids and indices into the
> >> answers arrays such as in the example above you'd want to prevent
> >> an entry at index 7 when there is no entry  in the questions
> >> table for question_id=7.
> >
> > It occurs to me that it shouldn't be terribly difficult to make an
> > alternate version of crosstab() that returns an array rather than
> > tuples  (back when crosstab() was first written, Postgres didn't
> > support NULL  array elements). Is this worth considering for 8.4?
>
> How about returning generic rows?  Is that possible?

One hack I've used in the past to get those is serializing the rows:
XML, YAML and most recently JSON.

> It would be really neat if you didn't have to specify the return
> type in the query that invoked the crosstab.

It would be handy :)

Cheers,
David.
--
David Fetter <david@fetter.org> http://fetter.org/
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