From: Bruce Momjian <pgman@candle.pha.pa.us>
Message-Id: <200409102148.i8ALmU129696@candle.pha.pa.us>
Subject: Re: aggregate function stddev
In-Reply-To: <200409091137.19204.josh@agliodbs.com>
To: Josh Berkus <josh@agliodbs.com>
Date: Fri, 10 Sep 2004 17:48:30 -0400 (EDT)
Cc: Kemin Zhou <kemin.zhou@ferring.com>, pgsql-sql@postgresql.org
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Type: text/plain; charset=US-ASCII


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) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073