May be this function can help :
http://www.postgresql.org/docs/8.3/static/functions-srf.html
Ries
On Oct 15, 2008, at 1:44 PM, Mark Morgan Lloyd wrote:
> Is there an easy way to assign a sequential number, possibly based
> on an arbitrary minimum (typically 0 or 1) to each row of an ordered
> result set, or do I have to work with explicit sequences?
>
> I need to do quite a lot of maths on successive rows, extracting
> numeric and timestamp differences hence rates of change. I've
> typically been doing it manually or in a spreadsheet but there has
> to be a better way e.g. by a join on offset row numbers.
>
> --
> Mark Morgan Lloyd
> markMLl .AT. telemetry.co .DOT. uk
>
> [Opinions above are the author's, not those of his employers or
> colleagues]
>
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