X-Original-To: pgsql-sql@postgresql.org
Received: from serwer.skawsoft.com.pl (serwer.skawsoft.com.pl [213.25.37.66])
	by postgresql.org (Postfix) with ESMTP id 7F65E47611A
	for <pgsql-sql@postgresql.org>; Thu,  6 Mar 2003 07:16:03 -0500 (EST)
Received: from klaster.net (pc126.krakow.cvx.ppp.tpnet.pl [213.76.38.126])
	by serwer.skawsoft.com.pl (Postfix) with ESMTP
	id 6C2E12B898; Thu,  6 Mar 2003 12:58:22 +0100 (CET)
Message-ID: <3E673874.5030606@klaster.net>
Date: Thu, 06 Mar 2003 13:00:52 +0100
From: Tomasz Myrta <jasiek@klaster.net>
User-Agent: Mozilla/5.0 (Windows; U; Win 9x 4.90; PL; rv:1.1) Gecko/20020826
X-Accept-Language: pl, en-us, en
MIME-Version: 1.0
To: Rajesh Kumar Mallah <mallah@trade-india.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: sql question regarding count(*)
References: <200303061702.26339.mallah@trade-india.com>
Content-Type: text/plain; charset=us-ascii; format=flowed
Content-Transfer-Encoding: 7bit
X-Archive-Number: 200303/167
X-Sequence-Number: 12207

Rajesh Kumar Mallah wrote:
> When does count(*) returns "o rows" ?
> and when does it return 1 row value being 0.
> 
> tradein_clients=# SELECT count(*)   from public.eyp_listing  where sno> 0 and 
> amount> 0  group by sno,branch,edition having count(distinct userid) > 1 ;
>  count
> -------
> (0 rows)
> 
> tradein_clients=#
> tradein_clients=#
> tradein_clients=# SELECT count(*) from public.users where userid=-1;
>  count
> -------
>      0
> (1 row)
> 
> tradein_clients=#
It's because of your having clause.
If count(*)=0 then having count(*)>1 results in no rows.

Regards,
Tomasz Myrta