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</o:shapelayout></xml><![endif]--></head><body lang=FR link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Hello,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>I’m not sure to understand what you are trying to do. Do you want to find the area of polygons from layer 1 which don’t contain any polygon from layer 2 or the difference between l1 and l2 (l1 – intersection(l1,l2)) ?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Hugues.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0cm 0cm 0cm'><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>De :</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> postgis-users-bounces@lists.osgeo.org [mailto:postgis-users-bounces@lists.osgeo.org] <b>De la part de</b> Cedric Duprez<br><b>Envoyé :</b> mardi 21 mai 2013 18:55<br><b>À :</b> PostGIS Users Discussion<br><b>Objet :</b> [postgis-users] Area of non-intersecting parts of layers<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'>Hi all,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Arial","sans-serif"'><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial","sans-serif"'>I have 2 layers composed of multipolygons in Postgis 2.0. Each layer contains polygons with a name that is sometime common to several polygons.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB style='font-size:10.0pt;font-family:"Arial","sans-serif"'>When I try to find area of intersections between the 2 layers, no problem with the following query:<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB>SELECT l1.name1, l2.name2, SUM(ST_Area(ST_Intersection(l1.geom, l2.geom))) / 10000 AS surface_ha<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB>FROM layer1 l1<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB>INNER JOIN layer2 l2 ON ST_Intersects(l1.geom, l2.geom)<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB>GROUP BY 1, 2<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB>ORDER BY 1, 2;<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB>OK.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB>But I also try to get the area of my layer1 (grouped by name1) that does not contain elements of my layer2.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB>I tried with LEFT JOIN, with ST_CONTAINS, without success.<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB>Does anyone have an idea on how to write this query?<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB>Thanks in advance,<o:p></o:p></span></p><p class=MsoNormal><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal><span lang=EN-GB>Cedric Duprez<o:p></o:p></span></p></div></body></html>