stdifference-geometry-data-type.md

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

STDifference (geometry Data Type)

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

Returns an object that represents the point set from one geometry instance that does not lie within another geometry instance.

Syntax

  
.STDifference ( other_geometry )  

Arguments

other_geometry
Is another geometry instance indicating which points to remove from the instance on which STDifference() 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 difference between two Polygon instances

The following example uses STDifference() to compute the difference between two polygons.

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.STDifference(@h).ToString();  

B. Invoking STDifference() on a CurvePolygon instance

The following example uses STDifference() on a CurvePolygon instance.

 DECLARE @g geometry = 'CURVEPOLYGON (CIRCULARSTRING (0 -4, 4 0, 0 4, -4 0, 0 -4))';  
 DECLARE @h geometry = 'POLYGON ((1 -1, 5 -1, 5 3, 1 3, 1 -1))';  
 -- Note the different results returned by the two SELECT statements  
 SELECT @h.STDifference(@g).ToString(), @g.STDifference(@h).ToString();

See Also

OGC Methods on Geometry Instances