[postgis-users] ESRI union (analysis) in Postgis

[Teresa Fazio]

I would like to perform in PostGIS a processing like that performed by 
the union(analysis) tool of ArcGIS.
See here reference
http://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=Union_(Analysis) 
<http://webhelp.esri.com/arcgisdesktop/9.2/index.cfm?TopicName=Union_%28Analysis%29> 


It is very difficult to add some words to what it does, so I've attached 
two layers before and after the union.

This tool repeats the new created geometries as many times as the number 
of the geometries which partecipate to the intersection, populating the 
attribute table with the relative generating geometry values.
So, after its execution, it allows you to perform a sum on a column 
attribute grouping by geometry.

Maybe such an operation could be generated using aotmic PostGIS operators.

Thank you very much
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