Re: Interpolation problem - pg 12.4 - full correct version!

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От David G. Johnston
Тема Re: Interpolation problem - pg 12.4 - full correct version!
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Msg-id CAKFQuwbdFn-4EkWsc27WGrKS2VK5Y4eF1TZVEwaB_ttpQz=ZYA@mail.gmail.com
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Ответ на Interpolation problem - pg 12.4 - full correct version!  (Pól Ua Laoínecháin <linehanp@tcd.ie>)
Ответы Re: Interpolation problem - pg 12.4 - full correct version!  (Joe Conway <mail@joeconway.com>)
Re: Interpolation problem - pg 12.4 - full correct version!  (Pól Ua Laoínecháin <linehanp@tcd.ie>)
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On Wed, Aug 19, 2020 at 11:51 AM Pól Ua Laoínecháin <linehanp@tcd.ie> wrote:

I think my *MAJOR* problem is that I've developed what is,
essentially, a totally brute force approach - and this simply won't
work at the scenario becomes more complex - take a look at the CASE
statement - it's horrible and would only become exponentially worse as
the number NULLs rises.

So, my question is: Is there a recognised technique (using SQL only,
not PL/pgSQL - soutions based on the latter are easy to find) whereby
I can do a basic Linear Interpolation?


I don't have a recognized technique, nor care to ponder one right now, but what you've described would best be done in pure SQL using WITH RECURSIVE, which provides an iterative approach to SQL result building.  Which is more commonly done in a procedural language.  The algorithm you describe is an iterative algorithm and so I'm wondering why place the arbitrary restriction on using pure SQL when it likely wouldn't provide a very readable nor performant solution relative to a procedural (pl/pgsql or otherwise) one?

David J.

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