Re: Table filter
От | Reg Me Please |
---|---|
Тема | Re: Table filter |
Дата | |
Msg-id | 200711212144.23111.regmeplease@gmail.com обсуждение исходный текст |
Ответ на | Re: Table filter (Joe Conway <mail@joeconway.com>) |
Ответы |
Re: Table filter
|
Список | pgsql-general |
Il Wednesday 21 November 2007 20:22:46 Joe Conway ha scritto: > 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 This is a good point. I just need to avoid doing crosstabs over a very large t_data: I fear it'd kill the application. -- Reg me Please <Non quietis maribus nauta>
В списке pgsql-general по дате отправления: