[postgis-users] Union and Intersection of polygons

[RAVI KUMAR]

Hi,
do we have 
UNION of Polygon layers:
where in two polygon layers are subjected to overlay analysis which results in joining both, with addition of attribute columns.
 Where the polygons intersect. both layers will have attributes written. 
 Where the polygons do not, intersect, both layers will have attributes null 
 for that layer. 
INTERSECTION of Polygon layers:
where in two polygon layers subjected to overlay analysis results in joining both, with addition of attribute columns only where polygons intersect. The non intersecting polygons are not written to the result.

Cheers
Ravi kumar