ST_SymDifference

Calculates all the points in two GEOMETRY objects except for the points they have in common, but including the boundaries of both objects.

This result is called the symmetric difference and is represented mathematically as: Closure (g1 – g2) È Closure (g2 – g1)

Behavior type

Syntax

ST_SymDifference( g1, g2 )

Arguments

g1

Spatial object, type GEOMETRY

g2

Spatial object, type GEOMETRY

Returns

GEOMETRY

Supported data types

Examples

The following examples show how to use ST_SymDifference.

Returns the two linestrings:

=> SELECT ST_AsText(ST_SymDifference(ST_GeomFromText('LINESTRING(30 40,
   30 55)'),ST_GeomFromText('LINESTRING(30 32.5,30 47.5)')));
    ST_AsText
-----------------
MULTILINESTRING ((30 47.5, 30 55),(30 32.5,30 40))
(1 row)

Returns four squares:

=> SELECT ST_AsText(ST_SymDifference(ST_GeomFromText('POLYGON((2 1,2 4,3 4,
   3 1,2 1))'),ST_GeomFromText('POLYGON((1 2,1 3,4 3,4 2,1 2))')));
                                ST_AsText
-------------------------------------------------------------------------
 MULTIPOLYGON (((2 1, 2 2, 3 2, 3 1, 2 1)), ((1 2, 1 3, 2 3, 2 2, 1 2)),
 ((2 3, 2 4, 3 4, 3 3, 2 3)), ((3 2, 3 3, 4 3, 4 2, 3 2)))
(1 row)