ST_Union

Calculates the union of all points in two spatial objects.

Calculates the union of all points in two spatial objects.

This result is represented mathematically by: g1 È g2

Behavior type

Immutable

Syntax

ST_Union( g1, g2 )

Arguments

g1
Spatial object, type GEOMETRY
g2
Spatial object, type GEOMETRY

Returns

GEOMETRY

Supported data types

Data Type GEOMETRY
Point Yes
Multipoint Yes
Linestring Yes
Multilinestring Yes
Polygon Yes
Multipolygon Yes
GeometryCollection Yes

Examples

The following example shows how to use ST_Union.

Returns a polygon that represents all the points contained in these two polygons:

=> SELECT ST_AsText(ST_Union(ST_GeomFromText('POLYGON((0 2,1 1,0 -1,-1 1,0 2))'),
   ST_GeomFromText('POLYGON((-1 2, 0 0, -2 0, -1 2))')));
                                     ST_AsText
------------------------------------------------------------------------------
 POLYGON ((0 2, 1 1, 0 -1, -0.5 0, -2 0, -1 2, -0.666666666667 1.33333333333, 0 2))
(1 row)