2010/4/5 Kevin Grittner <Kevin.Grittner@wicourts.gov>:
> Robert Haas <robertmhaas@gmail.com> wrote:
>
>> You can do:
>>
>> SELECT COUNT(*) FROM (SELECT DISTINCT profile.id, profile.name,
>> profile.age FROM ...) x;
>
> Ah, I see what they wanted now. In older versions of PostgreSQL,
> they might get better performance in some cases by using GROUP BY:
>
> SELECT COUNT(*) FROM
> (SELECT id, name, age FROM profile GROUP BY id, name, age) x;
>
> I don't remember offhand what version started considering a hash for
> DISTINCT.
>
8.4
http://www.postgresql.org/docs/8.4/static/release-8-4.html
regards
Pavel
> -Kevin
>
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