Re: Table filter

From: Joe Conway <mail(at)joeconway(dot)com>
To: Reg Me Please <regmeplease(at)gmail(dot)com>
Cc: pgsql-general(at)postgresql(dot)org
Subject: Re: Table filter
Date: 2007-11-21 19:22:46
Message-ID: 47448586.6050107@joeconway.com
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Reg Me Please wrote:

> The meaning is that an entity called by the value of "item" has a number
> of properties called by "property" with value "prop_value".
> So, for a single "item" there can be many different "property" each with its
> own value.

> A filter is a list of property values needed to qualify an entity as
> "good". An entity evaluates as good only when all property values in the
> filter match the ones associated to an item in t_data.
>
> What's missing to me is how to apply a filter to the t_data and get the list
> of the items that evaluate good.

I haven't played with it myself, but it seems to me that you could do
this with an inner join of two crosstabs -- one on t_data and one on the
filters (i.e. you join on the columns of the filter crosstab to the
matching ones in the t_data crosstab).

Joe

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