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;