%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" ...
As to why the "WHERE" clause? Perhaps this example is not trying to create a Voroni diagram for their entire database, but only for a relatively small number of rows. 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. That said, I haven't used the referred function so I may be misleading with the best of intentions. :-} HTH, Greg Williamson ________________________________ From: ΑΠΟΣΤΟΛΟΣ ΛΕΛΕΝΤΖΗΣ <[email protected]> To: PostGIS Users Discussion <[email protected]> Sent: Tue, March 8, 2011 2:50:07 AM Subject: [postgis-users] Create Voronoi Diagrams Hello everybody For another time, i ask your help and your experience!! Specifically, i want to create voronoi diagrams with postgis, and i found the following intersting link http://www.bostongis.com/PrinterFriendly.aspx?content_name=postgresql_plr_tut02 So, i have installed the pl/r language and i have run the voronoi function. But, i don't understand what kind of my data i have to place, at the below line code WHERE town = ''BOSTON'' AND grades LIKE ''%3%'' AND type = ''PUB'' why the writer use a WHERE statement ?? what does mean the variable "%3%" ?? Thankss
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