<html xmlns:v="urn:schemas-microsoft-com:vml" xmlns:o="urn:schemas-microsoft-com:office:office" xmlns:w="urn:schemas-microsoft-com:office:word" xmlns:m="http://schemas.microsoft.com/office/2004/12/omml" xmlns="http://www.w3.org/TR/REC-html40"><head><meta http-equiv=Content-Type content="text/html; charset=iso-8859-1"><meta name=Generator content="Microsoft Word 15 (filtered medium)"><!--[if !mso]><style>v\:* {behavior:url(#default#VML);}
o\:* {behavior:url(#default#VML);}
w\:* {behavior:url(#default#VML);}
.shape {behavior:url(#default#VML);}
</style><![endif]--><style><!--
/* Font Definitions */
@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}
@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}
/* Style Definitions */
p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
margin-bottom:.0001pt;
font-size:11.0pt;
font-family:"Calibri",sans-serif;}
a:link, span.MsoHyperlink
{mso-style-priority:99;
color:#0563C1;
text-decoration:underline;}
a:visited, span.MsoHyperlinkFollowed
{mso-style-priority:99;
color:#954F72;
text-decoration:underline;}
span.EmailStyle17
{mso-style-type:personal;
font-family:"Calibri",sans-serif;
color:windowtext;}
span.EmailStyle18
{mso-style-type:personal-reply;
font-family:"Calibri",sans-serif;
color:#1F497D;}
.MsoChpDefault
{mso-style-type:export-only;
font-size:10.0pt;}
@page WordSection1
{size:8.5in 11.0in;
margin:70.85pt 70.85pt 70.85pt 70.85pt;}
div.WordSection1
{page:WordSection1;}
--></style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]--></head><body lang=EN-US link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal><span style='color:#1F497D'>If you are running PostGIS 2.3 or above, I think ST_ClusterDBSCAN might do the trick for you:<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><a href="http://postgis.net/docs/manual-2.3/ST_ClusterDBSCAN.html">http://postgis.net/docs/manual-2.3/ST_ClusterDBSCAN.html</a><o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>You can set distance to 0 and minpoints to 2. All points that are not 0 distance from any other point will have NULL in the bucket column.<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>All other ones that have bucket numbers are duplicated.<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>So:<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>SELECT n.code, n.geom, ST_ClusterDBSCAN(n.geom, 0,2) AS bucket<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>FROM nodes <o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>If you want the counts instead of the bucket, you can do<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>SELECT o.code, o.geom, COUNT(*) OVER(PARTITION BY bucket) AS npoints, bucket<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>FROM (SELECT n.code, n.geom, ST_ClusterDBSCAN(n.geom, 0,2) AS bucket<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>FROM nodes ) AS o<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>WHERE bucket IS NOT NULL;<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>I didn't test so I might have a typo.<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Hope that helps,<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'>Regina<o:p></o:p></span></p><p class=MsoNormal><span style='color:#1F497D'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #E1E1E1 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal style='margin-left:.5in'><b>From:</b> postgis-users [mailto:postgis-users-bounces@lists.osgeo.org] <b>On Behalf Of </b>Olivier Leprêtre<br><b>Sent:</b> Wednesday, August 02, 2017 3:28 PM<br><b>To:</b> postgis-users@lists.osgeo.org<br><b>Subject:</b> [postgis-users] duplicated nodes<o:p></o:p></p></div></div><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p><p class=MsoNormal style='margin-left:.5in'><span lang=FR>Hi,<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span lang=FR><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span lang=EN-GB>I have a point layer that contains several superposed nodes two, three times or more. I would like to display each group list and the number of item in each. I found this query which “works” but returns some false positive<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span lang=EN-GB>select case when lag(o.geom) OVER (PARTITION BY o.geom) = o.geom then '' else 'x ' || o.nbre::text end,d.code from<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span lang=EN-GB>(select geom,count(*) as nbre from nodes group by geom having count(*) >1) as o,<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span lang=EN-GB>lateral (select * from nodes) as d where st_within(o.geom,d.geom)<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span lang=EN-GB>I understand that false positives (yellow beneath) comes from “group by geom” which use a bounding box and catch close but not duplicated points.<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span lang=FR><img border=0 width=90 height=191 id="Image_x0020_1" src="cid:image002.jpg@01D30BB1.F49CCCB0"></span><span lang=EN-GB><o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span lang=EN-GB>I tried other solutions which all get too complicated with several “join of join”. I would appreciate if someone has an idea on the top of his/her head !<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span lang=EN-GB>Thanks<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span lang=EN-GB><o:p> </o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span lang=EN-GB>Olivier<o:p></o:p></span></p><p class=MsoNormal style='margin-left:.5in'><span lang=EN-GB><o:p> </o:p></span></p></div></body></html>