ST_Union
Calculates the union of all points in two spatial objects.
This result is represented mathematically by: g1 È g2
Behavior Type
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 |
Example
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)