-- The example creates the convexhull_test table that has two columns:
-- geotype and g1. Geotype, a varchar(20), stores the name of the geometry
-- subclass that is stored in g1, a geometry.

CREATE TABLE convexhull_test (geotype varchar(20),
                              g1      ST_Geometry);

-- The INSERT statements insert several geometry subclasses
-- into the convexhull_test table.

INSERT INTO convexhull_test VALUES( 
   'Point',
   ST_PointFromText('point (10.02 20.01)',1000) 
);

INSERT INTO convexhull_test VALUES( 
   'Linestring', 
   ST_LineFromText('linestring (10.02 20.01,10.32 23.98,11.92 25.64)',1000) 
);

INSERT INTO convexhull_test VALUES(
   'Polygon',
   ST_PolyFromText('polygon ((10.02 20.01,11.92 35.64,25.02 34.15, 19.15 33.94,10.02 20.01))',1000) 
);

INSERT INTO convexhull_test VALUES( 
   'MultiPoint',
   ST_MPointFromText('multipoint (10.02 20.01,10.32 23.98,11.92 25.64)',1000)
);

INSERT INTO convexhull_test VALUES( 
   'MultiLineString',
   ST_MLineFromText('multilinestring ((10.02 20.01,10.32 23.98,11.92 25.64),(9.55 23.75,15.36 30.11))',1000)
);

INSERT INTO convexhull_test VALUES( 
   'Multipolygon', 
   ST_MPolyFromText('multipolygon (((10.02 20.01,11.92 35.64,25.02 34.15,19.15 33.94,10.02 20.01)),((51.71 21.73,73.36 27.04,71.52 32.87,52.43 31.90,51.71 21.73)))',1000)
);

-- The select statement lists the subclass name stored in the
-- geotype column and the convex hull. 

SELECT geotype, ST_ConvexHull(g1) convexhull 
   FROM convexhull_test;