Changes between Initial Version and Version 1 of UsersWikiExamplesJoinTables

Timestamp:

Apr 14, 2009, 8:54:39 AM (15 years ago)

Author:

pierre

Comment:

—

UsersWikiExamplesJoinTables

@@ +1 @@
+= Examples Join Tables =
+
+
+An attribute join is often needed when you need to associate a tabular data source with features. A left join is appropriate in this case since we want to retain all the spatial features and append the tabular attributes only where a match occurs.
+
+For example, lets say we have two tables:
+
+ * parcel  (with an "id" column and spatial geometry)
+ * owner (with an "id" column and owner information for that parcel id)
+
+----
+
+
+{{{
+CREATE TABLE parceljoin (id integer, ownername text);
+
+SELECT AddGeometryColumn('public', 'parceljoin','the_geom','4326','POLYGON',2);
+
+INSERT INTO parceljoin
+SELECT p.id as id, o.ownername as ownername, p.the_geom as the_geom
+FROM parcel p
+LEFT JOIN owners o ON o.id = p.id;
+
+}}}