From: Thomas F.O'Connell <tfo@sitening.com>
To: Stephan Szabo <sszabo@megazone.bigpanda.com>
Cc: PgSQL - SQL <pgsql-sql@postgresql.org>
Subject: Re: Counting Distinct Records
Date: Wed, 17 Nov 2004 13:27:17 -0600
Message-ID: <B16EB296-38CE-11D9-95C2-000D93AE0944@sitening.com> (raw)
In-Reply-To: <20041117064813.V17486@megazone.bigpanda.com>
References: <1B2F7B00-3808-11D9-95C2-000D93AE0944@sitening.com>
<20041116115807.E79990@megazone.bigpanda.com>
<6E79C2FE-380B-11D9-95C2-000D93AE0944@sitening.com>
<20041116141911.K84773@megazone.bigpanda.com>
<A72D6B26-3823-11D9-95C2-000D93AE0944@sitening.com>
<20041117064813.V17486@megazone.bigpanda.com>
The specific problem I'm trying to solve involves a user table with
some history.
Something like this:
create table user_history (
user_id int
event_time_stamp timestamp
);
I'd like to be able to count the distinct user_ids in this table, even
if it were joined to other tables.
-tfo
--
Thomas F. O'Connell
Co-Founder, Information Architect
Sitening, LLC
http://www.sitening.com/
110 30th Avenue North, Suite 6
Nashville, TN 37203-6320
615-260-0005
On Nov 17, 2004, at 8:52 AM, Stephan Szabo wrote:
> On Tue, 16 Nov 2004, Thomas F.O'Connell wrote:
>
>> Hmm. I was more interested in using COUNT( * ) than DISTINCT *.
>>
>> I want a count of all rows, but I want to be able to specify which
>> columns are distinct.
>
> I'm now a bit confused about exactly what you're looking for in the
> end.
> Can you give a short example?
>
>> That's definitely an interesting approach, but testing doesn't show it
>> to be appreciably faster.
>>
>> If I do a DISTINCT *, postgres will attempt to guarantee that there
>> are
>> no duplicate values across all columns rather than a subset of
>> columns?
>> Is that right?
>
> It guarantees one output row for each distinct set of column values
> across
> all columns.
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To: pgsql-sql@postgresql.org
Cc: tfo@sitening.com, sszabo@megazone.bigpanda.com
Subject: Re: Counting Distinct Records
In-Reply-To: <B16EB296-38CE-11D9-95C2-000D93AE0944@sitening.com>
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