[postgis-users] how to create holes in polygon

[Kevin Kempfer]

Hi,

I am trying to punch holes into a polygon - can someone tell me how to
achieve this?

I have a large database of polygon geometries.
I am now trying to "invert" these polygons area to receive a big
polygon, that covers everything that is *not* covered in my existing
polygons.

The result should be a polygon covering the whole world but with holes
in the areas which are already covered by my source polygons.

I successfully created a "positive" using geomunion() on all my geoms.
Now I need to invert the result  to get a "negative". Hope I got the
idea across...

Thanks for any advice,

Kevin