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

From Tom Lane
Subject Re: No stddev() for interval?
Date
Msg-id 11541.1148142887@sss.pgh.pa.us
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In response to Re: No stddev() for interval?  ("Ivan Zolotukhin" <ivan.zolotukhin@gmail.com>)
Responses Re: No stddev() for interval?  ("Nikolay Samokhvalov" <samokhvalov@gmail.com>)
List pgsql-general
"Ivan Zolotukhin" <ivan.zolotukhin@gmail.com> writes:
> On 5/20/06, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Is it sensible to calculate standard deviation on intervals?  How would
>> you handle the multiple components?  I mean, you could certainly define
>> *something*, but how sane/useful would the result be?

> Strictly speaking there's nothing bad in intervals. Physically
> standart deviation on interval can be very useful without any doubts.

If the intervals are all expressed in seconds then sure, the calculation
is straightforward and useful.  I'm wondering what happens when nonzero
values of days and months get in there.

            regards, tom lane

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