STUnion (geometry Data Type)

Article
05/23/2023

Applies to: SQL Server Azure SQL Database Azure SQL Managed Instance SQL analytics endpoint in Microsoft Fabric Warehouse in Microsoft Fabric

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

Syntax

  
.STUnion ( other_geometry )

Note

To view Transact-SQL syntax for SQL Server 2014 (12.x) and earlier versions, see Previous versions documentation.

Arguments

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

Return Types

SQL Server 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.