Re: Counting Distinct Records

The specific problem I'm trying to solve involves a user table with 
some history.

Something like this:

create table user_history (user_id intevent_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.