ST_Relate

ST_Relate takes two geometries and a Dimensionally Extended 9 Intersection Model (DE-9IM) matrix as input parameters and returns 1 if the given geometries meet the conditions specified by the matrix. Otherwise, 0 (zero) is returned.

If any of the given geometries is null or empty, then null is returned.

If the second geometry is not represented in the same spatial reference system as the first geometry, the second geometry will be converted to the other spatial reference system.

Syntax

Parameters

geometry1: A value of one of the seven distinct spatial data types that represents the geometry that is tested against geometry2.
geometry2: A value of one of the seven distinct spatial data types that represents the geometry that is tested against geometry1.
matrix: A value of CHAR(9) that represents the DE-9IM matrix that is to be used for the test of geometry1 and geometry2.

Return type

INTEGER

Example

The following example creates two separate polygons. Then, the ST_Relate function is used to determine several relationships between the two polygons. For example, whether the two polygons overlap.


SET CURRENT FUNCTION PATH = CURRENT FUNCTION PATH, db2gse
CREATE TABLE sample_polys (id INTEGER, geometry ST_Polygon)

INSERT INTO sample_polys
  VALUES (1,
          ST_Polygon('polygon ( (40 120, 90 120, 90 150, 40 150, 40 120) )', 0))
INSERT INTO sample_polys
  VALUES (2,
          ST_Polygon('polygon ( (30 110, 50 110, 50 130, 30 130, 30 110) )', 0))

SELECT ST_Relate(a.geometry, b.geometry, CHAR('T*T***T**')  "Overlaps  ",
       ST_Relate(a.geometry, b.geometry, CHAR('T*T***FF*')  "Contains  ",
       ST_Relate(a.geometry, b.geometry, CHAR('T*F**F***')  "Within    "
       ST_Relate(a.geometry, b.geometry, CHAR('T********')  "Intersects",
       ST_Relate(a.geometry, b.geometry, CHAR('T*F**FFF2')  "Equals    "
  FROM sample_polys a, sample_polys b
  WHERE a.id = 1 AND b.id = 2

Results:



Overlaps    Contains    Within      Intersects  Equals
----------- ----------- ----------- ----------- -----------
          1           0           0           1           0