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Re: No stddev() for interval? - Mailing list pgsql-general

From David Fetter
Subject Re: No stddev() for interval?
Date
Msg-id 20060520202828.GA27076@fetter.org
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In response to No stddev() for interval?  ("Brendan Jurd" <direvus@gmail.com>)
Responses Re: No stddev() for interval?  ("Brendan Jurd" <direvus@gmail.com>)
Re: No stddev() for interval?  ("Nikolay Samokhvalov" <samokhvalov@gmail.com>)
List pgsql-general
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On Sun, May 21, 2006 at 01:14:15AM +1000, Brendan Jurd wrote:
> Hi all,
>
> I noticed a peculiarity in the default postgres aggregate functions.  min(),
> max() and avg() support interval as an input type, but stddev() and
> variance() do not.
>
> Is there a rationale behind this, or is it just something that was never
> implemented?

That's because variance of foo is measured in foo^2 units.  What is
the square of an interval?

Cheers,
D
--
David Fetter <david@fetter.org> http://fetter.org/
phone: +1 415 235 3778        AIM: dfetter666
                              Skype: davidfetter

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