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)