STDifference (geometry Data Type)

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 point set from one geometry instance that does not lie within another geometry instance.


.STDifference ( other_geometry )  


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


Is another geometry instance indicating which points to remove from the instance on which STDifference() is being invoked.

Return Types

SQL Server return type: geometry

CLR return type: SqlGeometry


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.


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