Toby, I agree with Stanley that it is probably not a ST_Union problem. I'm guessing there is something wrong with your WHERE clause. Keep in mind PostgreSQL is case sensitive so if by chance you had something like ln1 instead of LN1 in the com_dist field, then the ln1s would be picked up as NOT .... To rule out ST_Union as the culprit, can you do a simple attribute query SELECT postarea, com_dist, gid FROM postcode_sectors WHERE postarea = 'LN' AND NOT com_dist = 'LN1' ORDER BY postarea, com_dist Also I tend to do com_dist <> 'LN1' , but that shouldn't matter. Hope that helps, Regina
_____ From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Toby Rainthorpe Sent: Saturday, November 01, 2008 2:19 PM To: PostGIS Users Discussion Subject: Re: [postgis-users] Union, but need to exclude any void Sadly it doesn't work, here is a search for the post code area LN, but excluding LN1. This should give the polygon of lincoln, with the exception of the town centre district. Instead it creates a polygon for the whole LN post area. Just to clarify, I do want the hole in a polygon. SELECT ST_AsKML(ST_Union(the_geom)) as the_geom FROM postcode_sectors WHERE postarea = 'LN' AND NOT com_dist = 'LN1' <?xml version="1.0" encoding="UTF-8"?> <kml xmlns="http://www.opengis.net/kml/2.2";> <Placemark> <Polygon><outerBoundaryIs><LinearRing><coordinates>-0.574252637693809,53.235 9726746639 -0.570638045173646,53.2342660459289 -0.567956817933028,53.233334871246 -0.542511758566372,53.2276409117944 -0.539261287526225,53.2285001962972 -0.537587144360509,53.23365835124 -0.536621729986015,53.2443903523506 -0.538372820842824,53.2545802514289 -0.53867243559146,53.2902048795337 -0.541250872030082,53.3316560575988 -0.567075865458079,53.3529438083222 -0.549064460589285,53.4257467252708 -0.461252440918993,53.4290079476242 -0.459280037729661,53.4356804144195 -0.491910432874966,53.497600359203 -0.41389940584748,53.5500565803702 -0.310449877650045,53.5267476031091 -0.219352544114183,53.5272954168687 -0.215026390840363,53.5063814691382 -0.203265094143773,53.466744705434 -0.122544300870874,53.4548941206983 0.0264268890418949,53.4620080919002 0.083849617015283,53.496544395631 0.228359151391426,53.408400422663 0.268028563946318,53.342544544341 0.302708719734213,53.2940795243504 0.321850405882593,53.2715163271867 0.234840151689661,53.1942224753385 0.194430850648443,53.213308161178 0.169714736355569,53.2124120839752 0.0834492984598471,53.2348844372266 0.0208307835734331,53.2478135975227 -0.0126938531249155,53.1710150547887 -0.13716904881661,53.1418544045366 -0.150749526290076,53.1243892073786 -0.130710137006856,53.0239835120991 -0.229285061035197,53.0038950480853 -0.338497757654447,53.0609112327498 -0.408675738441825,53.055621865059 -0.452241950934627,53.0579499714055 -0.52047527802287,53.0487392813369 -0.660214167307015,53.0546658032031 -0.714807399468163,53.0584148660486 -0.699290317426583,53.0756434022022 -0.716927624544292,53.1105928908201 -0.674018446595594,53.2187206490539 -0.668182682830745,53.2552110975952 -0.640114978977996,53.2538783112452 -0.574252637693809,53.2359726746639</coordinates></LinearRing></outerBoundar yIs></Polygon> </Placemark> </kml> From: [EMAIL PROTECTED] Subject: RE: [postgis-users] Union, but need to exclude any void Date: 1 November 2008 14:58:26 GMT To: postgis-users@postgis.refractions.net Reply-To: postgis-users@postgis.refractions.net 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: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] 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 ) _______________________________________________ postgis-users mailing list postgis-users@postgis.refractions.net http://postgis.refractions.net/mailman/listinfo/postgis-users _______________________________________________ postgis-users mailing list [EMAIL PROTECTED]
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