[postgis-users] Difference polygon sets

[Espen Isaksen]

Hi!

I have a set of polygons where I have dissolved some of the polygons.
So I get two sets of polygons where one set is my original data, and
the other set is new polygons from the dissolve operations. Now I want
to extract the remaining polygons from my original dataset which were
not dissolved. I tried just a simple st_difference, but from what I
understand this operation does now work on sets of polygons.

Both datasets can be found here in shape format:
http://dl.dropbox.com/u/8829/postgis.zip

How can I extract only the remaining polygons from the original
dataset. I had a look at this
post(http://www.postgis.org/pipermail/postgis-users/2008-May/019511.html)
in the mailing list, but I did not succeed in changing it to fit my
purpose.

Can anybody help me out?

Kind regards,
Espen Isaksen