<html><head><style type="text/css"><!-- DIV {margin:0px;} --></style></head><body><div style="font-family:arial,helvetica,sans-serif;font-size:12pt">%3% is looking for anything for a "3" in it -- similar to *3* so this would find every row for BOSTON with grades like .3, .03, 3.0, 1.3, 32, etc. that also have a type of "pub" ...<br><br>As to why the "WHERE" clause?<br><br>Perhaps this example is not trying to create a Voroni diagram for their entire database, but only for a relatively small number of rows.<br><br>Trying to create a Voroni diagram for a large data set will be slow and might exceed memory or other system resources, so unless your database is small, I'd try a subset of data, either limited by type or place name, or by a bounding box.<br><br>That said, I haven't used the referred function so I may be misleading with the best of intentions. :-}<br><br>HTH,<br><br>Greg Williamson<br><br><div><br></div><div style="font-family:
arial,helvetica,sans-serif; font-size: 12pt;"><br><div style="font-family: times new roman,new york,times,serif; font-size: 12pt;"><font face="Tahoma" size="2"><hr size="1"><b><span style="font-weight: bold;">From:</span></b> ΑΠΟΣΤΟΛΟΣ ΛΕΛΕΝΤΖΗΣ <lelentzisapostolos@gmail.com><br><b><span style="font-weight: bold;">To:</span></b> PostGIS Users Discussion <postgis-users@postgis.refractions.net><br><b><span style="font-weight: bold;">Sent:</span></b> Tue, March 8, 2011 2:50:07 AM<br><b><span style="font-weight: bold;">Subject:</span></b> [postgis-users] Create Voronoi Diagrams<br></font><br>
Hello everybody<br><br>For another time, i ask your help and your experience!!<br>Specifically, i want to create voronoi diagrams with postgis, and i found the following intersting link<br><span><a target="_blank" href="http://www.bostongis.com/PrinterFriendly.aspx?content_name=postgresql_plr_tut02">http://www.bostongis.com/PrinterFriendly.aspx?content_name=postgresql_plr_tut02</a></span><br>
So, i have installed the pl/r language and i have run the voronoi function.<br>But, i don't understand what kind of my data i have to place, at the below line code<br><span id="ctl00_cphMain_BodyContent">WHERE town = ''BOSTON'' AND grades LIKE ''%3%'' AND type = ''PUB''</span><br>
why the writer use a WHERE statement ?? <br>what does mean the variable "%3%" ??<br><br>Thankss<br>
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