Re: aggregate function stddev - Mailing list pgsql-sql

From Bruce Momjian
Subject Re: aggregate function stddev
Date
Msg-id 200409102148.i8ALmU129696@candle.pha.pa.us
Whole thread Raw
In response to Re: aggregate function stddev  (Josh Berkus <josh@agliodbs.com>)
List pgsql-sql
Is this a TODO?

---------------------------------------------------------------------------

Josh Berkus wrote:
> Kemin,
> 
> > Just noticed that the postgres stddev is the stddev_sample formula.
> > There are two different ways to calculate this value.
> > Their difference is very small with large samle size.  It would be nice
> > to distinguish the two different versions.
> 
> Note sent to PGSQL-DOCS.
> 
> > I also noticed that oracle has stddev_sample and stddev_population.
> > This is just a wish list.
> 
> Were you aware that in PostgreSQL you can write your own aggregates?   It's 
> relatively easy to do.
> 
> -- 
> Josh Berkus
> Aglio Database Solutions
> San Francisco
> 
> ---------------------------(end of broadcast)---------------------------
> TIP 9: the planner will ignore your desire to choose an index scan if your
>       joining column's datatypes do not match
> 

--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
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