X-Original-To: pgsql-sql-postgresql.org@localhost.postgresql.org Received: from localhost (unknown [200.46.204.144]) by svr1.postgresql.org (Postfix) with ESMTP id D5CE2329E17 for ; Thu, 9 Sep 2004 19:37:19 +0100 (BST) Received: from svr1.postgresql.org ([200.46.204.71]) by localhost (av.hub.org [200.46.204.144]) (amavisd-new, port 10024) with ESMTP id 43629-07 for ; Thu, 9 Sep 2004 18:37:16 +0000 (GMT) Received: from davinci.ethosmedia.com (server226.ethosmedia.com [209.128.84.226]) by svr1.postgresql.org (Postfix) with ESMTP id 0F6DC329E12 for ; Thu, 9 Sep 2004 19:37:16 +0100 (BST) Received: from [63.195.55.98] (HELO spooky) by davinci.ethosmedia.com (CommuniGate Pro SMTP 4.1.8) with ESMTP id 6312721; Thu, 09 Sep 2004 11:38:35 -0700 Content-Type: text/plain; charset="iso-8859-1" From: Josh Berkus Organization: Aglio Database Solutions To: Kemin Zhou , pgsql-sql@postgresql.org Subject: Re: aggregate function stddev Date: Thu, 9 Sep 2004 11:37:19 -0700 User-Agent: KMail/1.4.3 References: <413F758A.80306@ferring.com> In-Reply-To: <413F758A.80306@ferring.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Message-Id: <200409091137.19204.josh@agliodbs.com> X-Virus-Scanned: by amavisd-new at hub.org X-Spam-Status: No, hits=0.0 tagged_above=0.0 required=5.0 tests= X-Spam-Level: X-Archive-Number: 200409/64 X-Sequence-Number: 18910 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