| 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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| Thread: | |
| Lists: | pgsql-general | 
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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