ST_Union method for type ST

ST_Union method for type ST_Geometry

Returns the geometry value that represents the point set union of two geometries.

Syntax

geometry-expression.ST_Union(geo2)

Parameters

Name	Type	Description
geo2	ST_Geometry	The other geometry value that is to be unioned with the geometry-expression.

Returns

ST_Geometry Returns the geometry value that represents the point set union of two geometries.
The spatial reference system identifier of the result is the same as the spatial reference system of the geometry-expression.

Remarks

The ST_Union method finds the spatial union of two geometries. A point is included in the union if it is present in either of the two input geometries.

Note

If the geometry-expression contains circular strings, then these are interpolated to line strings.

Standards and compatibility

Example

The following example shows the union (C) of a square (A) and a circle (B).

SELECT NEW ST_Polygon( 'Polygon( (-1 -0.25, 1 -0.25, 1 2.25, -1 2.25, -1 -0.25) )' ) AS A
    , NEW ST_CurvePolygon( 'CurvePolygon( CircularString( 0 1, 1 2, 2 1, 1 0, 0 1 ) )' )  AS B
    , A.ST_Union( B ) AS C

The union is shaded in the following picture. The union is a single surface that includes all of the points that are in A or in B.

Discuss this page in DocCommentXchange.