stunion-geometry-data-type.md

title	description	author	ms.author	ms.date	ms.service	ms.subservice	ms.topic	f1_keywords	helpviewer_keywords	dev_langs	monikerRange
STUnion (geometry Data Type)	STUnion (geometry Data Type)	MladjoA	mlandzic	08/03/2017	sql	t-sql	reference	STUnion (geometry Data Type) STUnion_TSQL	STUnion (geometry Data Type)	TSQL	=azuresqldb-current||>=sql-server-2016||>=sql-server-linux-2017||=azuresqldb-mi-current||=fabric

STUnion (geometry Data Type)

[!INCLUDE SQL Server Azure SQL Database Azure SQL Managed Instance FabricSE FabricDW]

Returns an object that represents the union of a geometry instance with another geometry instance.

Syntax

  
.STUnion ( other_geometry )  

[!INCLUDEsql-server-tsql-previous-offline-documentation]

Arguments

other_geometry
Is another geometry instance to form a union with the instance on which STUnion() is being invoked.

Return Types

[!INCLUDEssNoVersion] return type: geometry

CLR return type: SqlGeometry

Remarks

This method always returns null if the spatial reference IDs (SRIDs) of the geometry instances do not match. The result may contain circular arc segments only if the input instances contain circular arc segments.

Examples

A. Computing the union of two Polygon instances

The following example uses STUnion() to compute the union of two Polygon instances.

DECLARE @g geometry;  
DECLARE @h geometry;  
SET @g = geometry::STGeomFromText('POLYGON((0 0, 0 2, 2 2, 2 0, 0 0))', 0);  
SET @h = geometry::STGeomFromText('POLYGON((1 1, 3 1, 3 3, 1 3, 1 1))', 0);  
SELECT @g.STUnion(@h).ToString();  

B. Computing the union of a Polygon instance with a CurvePolygon instance

The following example returns a GeometryCollection instance that contains a circular arc segment.

 DECLARE @g geometry = 'CURVEPOLYGON(CIRCULARSTRING(0 -4, 4 0, 0 4, -4 0, 0 -4))';  
 DECLARE @h geometry = 'POLYGON((5 -1, 5 -3, 7 -3, 7 -1, 5 -1))';  
 SELECT @g.STUnion(@h).ToString();

STUnion() returns a result that contains a circular arc segment because the instance that invoked STUnion() contains a circular arc segment.

See Also

OGC Methods on Geometry Instances