Changes between Version 2 and Version 3 of UsersWikiExamplesFindNearby

Timestamp:

Jul 8, 2009, 3:26:23 PM (15 years ago)

Author:

pramsey

Comment:

—

UsersWikiExamplesFindNearby

@@ -4 +4 @@
 One of the most common spatial SQL queries answers the question: "What are all the features within distance X of this other feature?"  In concrete terms: "How many cell towers are within 1km of my current location?" or "What are the schools within 5km of this house?"
 
-Taking the schools example as a template, here is a simple query to answer the question:
+For versions 1.3 and higher, the answer is very simple:
+
+{{{
+#!sql
+SELECT the_geom, school_name
+ FROM schools
+ WHERE st_dwithin(the_geom, 'POINT(100312 102312)',5000)
+
+}}}
+
+For older versions, you will have to hand-roll the query:
 
 {{{
@@ -31 +41 @@
 
 Note the new logical clause before the AND.  The && operator is the index operator, and represents a bounding box filter between the feature in the_geom and the comparison feature.  The Expand() function is a utility function that takes an existing feature and returns a new feature with a larger bounding box.  The result of this new query is to first use the index to find all features where the bounding boxes interact within a tolerance of 5km, then use the exact Distance() function to strip the final result set out of the intermediate bounding box result set.
-
-Newer way for version 1.3 and above
-
-{{{
-#!sql
-SELECT the_geom, school_name
- FROM schools
- WHERE st_dwithin(the_geom, 'POINT(100312 102312)',5000)
-
-}}}