Обсуждение: e: Running/cumulative count using windows

> test=*# select extract (year from signup_date)::text || '/' ||
extract(month from signup_date)::text, count(email_address),
sum(count(email_address)) over (ROWS UNBOUNDED PRECEDING) from test
group by 1 order by 1;

Have searched the manual and been unable to find reference to the
commands 'unbounded' and 'preceding'; can someone please advise where
to read about these commands?

On 12/09/2013, pgsql-general-owner@postgresql.org
<pgsql-general-owner@postgresql.org> wrote:
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On Fri, Sep 13, 2013 at 8:18 AM, e-letter <inpost@gmail.com> wrote:
>> test=*# select extract (year from signup_date)::text || '/' ||
> extract(month from signup_date)::text, count(email_address),
> sum(count(email_address)) over (ROWS UNBOUNDED PRECEDING) from test
> group by 1 order by 1;
>
> Have searched the manual and been unable to find reference to the
> commands 'unbounded' and 'preceding'; can someone please advise where
> to read about these commands?

http://www.postgresql.org/docs/9.1/static/sql-expressions.html#SYNTAX-WINDOW-FUNCTIONS

merlin