| From: | Stephan Szabo <sszabo(at)megazone(dot)bigpanda(dot)com> |
|---|---|
| To: | "Thomas F(dot)O'Connell" <tfo(at)sitening(dot)com> |
| Cc: | PgSQL - SQL <pgsql-sql(at)postgresql(dot)org> |
| Subject: | Re: Counting Distinct Records |
| Date: | 2004-11-17 14:52:54 |
| Message-ID: | 20041117064813.V17486@megazone.bigpanda.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-sql |
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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