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Subject: Re: Windowing ?
To: pgsql-sql@lists.postgresql.org
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From: Andreas Kretschmer <andreas@a-kretschmer.de>
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Date: Mon, 11 Dec 2017 18:15:56 +0100
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Am 11.12.2017 um 18:09 schrieb Olivier Leprêtre:
>
> Hi,
>
> I have a table describing sort of ordered road segments and their 
> associated weight. I would like to calculate weight deltas between two 
> consecutive segments. Problem is to substract previous from current 
> row and reuses result as input for the next row.
>

You can use the lag() - function.

select ..., lag(weight) over (partition by road order by segment) ...



Regards, Andreas

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