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GeometryCollection

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

A GeometryCollection is a collection of zero or more geometry or geography instances. A GeometryCollection can be empty.

GeometryCollection instances

Accepted instances

For a GeometryCollection instance to be accepted, it must either be an empty GeometryCollection instance or all the instances comprising the GeometryCollection instance must be accepted instances. The following example shows accepted instances.

DECLARE @g1 geometry = 'GEOMETRYCOLLECTION EMPTY';  
DECLARE @g2 geometry = 'GEOMETRYCOLLECTION(LINESTRING EMPTY,POLYGON((-1 -1, -1 -5, -5 -5, -5 -1, -1 -1)))';  
DECLARE @g3 geometry = 'GEOMETRYCOLLECTION(LINESTRING(1 1, 3 5),POLYGON((-1 -1, -1 -5, -5 -5, -5 -1, -1 -1)))';

The following example throws a System.FormatException because the LinesString instance in the GeometryCollection instance is not accepted.

DECLARE @g geometry = 'GEOMETRYCOLLECTION(LINESTRING(1 1), POLYGON((-1 -1, -1 -5, -5 -5, -5 -1, -1 -1)))';

Valid instances

A GeometryCollection instance is valid when all instances that comprise the GeometryCollection instance are valid. The following shows three valid GeometryCollection instances and one instance that is not valid.

DECLARE @g1 geometry = 'GEOMETRYCOLLECTION EMPTY';  
DECLARE @g2 geometry = 'GEOMETRYCOLLECTION(LINESTRING EMPTY,POLYGON((-1 -1, -1 -5, -5 -5, -5 -1, -1 -1)))';  
DECLARE @g3 geometry = 'GEOMETRYCOLLECTION(LINESTRING(1 1, 3 5),POLYGON((-1 -1, -1 -5, -5 -5, -5 -1, -1 -1)))';  
DECLARE @g4 geometry = 'GEOMETRYCOLLECTION(LINESTRING(1 1, 3 5),POLYGON((-1 -1, 1 -5, -5 5, -5 -1, -1 -1)))';  
SELECT @g1.STIsValid(), @g2.STIsValid(), @g3.STIsValid(), @g4.STIsValid();

@g4 is not valid because the Polygon instance in the GeometryCollection instance is not valid.

For more information on accepted and valid instances, see Point, MultiPoint, LineString, MultiLineString, Polygon, and MultiPolygon.

Example

The following example instantiates a geometry GeometryCollection with Z values in SRID 1 containing a Point instance and a Polygon instance.

DECLARE @g geometry;  
SET @g = geometry::STGeomCollFromText('GEOMETRYCOLLECTION(POINT(3 3 1), POLYGON((0 0 2, 1 10 3, 1 0 4, 0 0 2)))', 1);

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