-- A DE-9IM pattern matrix is a device for comparing geometries.
-- These are serveral types of such matrices. There are several
-- types of such matrices. For example, the equals pattern matrix
-- will tell you if any two geometries are equal.

-- In this example, an equals pattern matrix, shown below is read left
-- to right, and top to bottom into the string ("T*F**FFF*").
--
--                               b
--
--                  Interior  Boundary  Exterior
--         Interior     T         *         F
--    a    Boundary     *         *         F
--         Exterior     F         F         *
--

-- The table relate_test is created with the following CREATE TABLE statement.

CREATE TABLE relate_test (g1 ST_Geometry,
                          g2 ST_Geometry,
                          g3 ST_Geometry);

-- The following INSERT statements insert a sample subclass into the
-- relate_test table.

INSERT INTO relate_test VALUES(
   ST_PointFromText('point (10.02 20.01)',1000),
   ST_PointFromText('point (10.02 20.01)',1000),
   ST_PointFromText('point (30.01 20.01)',1000)
);

-- The following SELECT statement and the corresponding result
-- set demonstrates that the geometries which are equal match the
-- equals pattern matrix, and those which are not equal do not match.

SELECT ST_Relate(g1,g2,"T*F**FFF*") equals,
       ST_Relate(g1,g3,"T*F**FFF*") not_equals
   FROM relate_test;