[postgis-users] Union, but need to exclude any void

[Sufficool, Stanley]

I've never had a problem with st_union including holes when it
shouldn't. Your query syntax is a bit odd though. Maybe try the
following:

SELECT ST_Union(the_geom) as the_geom
FROM territories 
WHERE is_an_outer_territory = 1
 

> -----Original Message-----
> From: postgis-users-bounces at postgis.refractions.net 
> [mailto:postgis-users-bounces at postgis.refractions.net] On 
> Behalf Of Toby Rainthorpe
> Sent: Saturday, November 01, 2008 1:37 AM
> To: PostGIS Users Discussion
> Subject: [postgis-users] Union, but need to exclude any void
> 
> 
> I have a list of territories, say 9 represented by a tic, tac, toe   
> board (3 x 3 grid ). A query selects all the outer perimeter (8  
> territories), but omits the central block. If i were then to union  
> this group the resulting polygon would fill, or include this central  
> block, even though I have not exclusively said that that 
> territory has  
> been selected.
> 
> Is there a way of doing a union, or another method on a set of  
> polygons that will result in a polygon being created, but allow for  
> the void not to be included.
> 
> Thanks for your help,
> 
> Toby
> 
> 
> SELECT
> 	GeomUnion(geom) as the_geom,
> FROM (
> 	SELECT (dump(the_geom)).geom FROM territories WHERE  
> is_an_outer_territory = 1
> ) 
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