Re: how to effectively SELECT new "customers"

Jan Ostrochovsky wrote
> customer may have various payment channels during the time... new-ness is
> not impacted by the channel, it does not matter from which channel, all
> customer_id occurences count (in determined filtration criteria, e.g.
> town, service, subservice)
>
> and there are also other filtration and grouping criteria (town, service,
> subservice) and user of reporting tool should have possibility to select
> from those... there are dozens of services and subservices, cca 4 payment
> channels, dozens of towns... therefore preprocessing through materialized
> view (if I understand your suggestion correctly), would contain a lot of
> combinations, it seems quite complex for me in these circumstances
>
> I also considered WITH (CTEs) previously, I will rethink it yet, after
> these your recommendations

I'm not sure what you are going for since you keep adding additional
criteria/constraints to your problem. At this point you are faced with a
series of trade-offs between caching, speed, and flexibilty, complexity. I
would suggest you break up your requirements into smaller pieces and not go
looking for some kind of magic bullet that will solve all your problems in a
single query. It likely does not exist.

I would also suggest that you look into resources on data warehousing and
the star schema; doing what you are trying directly within the OLTP is
probably not the best solution - especially not on front-end servers. My
experience in this area is thin but maybe someone else can make some
suggestions and/or provide some useful resource links.

David J.

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