[postgis-users] subquery on a postgis layer

toni hernnadez thernandez at correo.giscampus.org
Mon Mar 13 02:04:19 PST 2006

I have several tables related with the urban planning in my town.
Two of these tables are:
Urban Soil 2006, and green areas 1992. Both have a geom field called 
"geom" and some other alfanumeric fields. There is no relation between 
these two tables.

I would like to show the intersection of these two layers to show which 
green areas have turn into urban soil.
I haven't either UNION nor JOIN. The thing is I don't know if this is 
possible and if so.. how to do it.

Markus Schaber wrote:

>Hi, Toni,
>toni hernnadez wrote:
>>Is it possible to use the intersection function (or any other spacial
>>postgis function) on two postgis tables with  a  postgis layer on
>Yes, it should be, but it's possible that you need to create a view and
>appropriate geometry_columns entry.
>For proper help, we need more details (do you UNION, JOIN or sub-SELECT
>the two tables together, what should intersect etc.).

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