UnionAggregate (geometry Data Type)

**APPLIES TO:** ![yes](media/yes.png)SQL Server (starting with 2012) ![yes](media/yes.png)Azure SQL Database ![no](media/no.png)Azure SQL Data Warehouse ![no](media/no.png)Parallel Data Warehouse

Performs a union operation on a set of geometry objects.

Syntax

  
UnionAggregate ( geometry_operand )

Arguments

geometry_operand
Is a geometry type table column that holds the set of geometry objects on which to perform a union operation.

Return Types

SQL Server return type: geometry

Exceptions

Throws a FormatException when there are input values that are not valid. See STIsValid (geometry Data Type)

Remarks

Method returns null when the input is empty or the input has different SRIDs. See Spatial Reference Identifiers (SRIDs)

Method ignores null inputs.

[!NOTE]
Method returns null if all inputted values are null.

Examples

The following example returns the union of a set of geometry objects in a table variable.
-- Setup table variable for UnionAggregate example DECLARE @Geom TABLE ( shape geometry, shapeType nvarchar(50) ); INSERT INTO @Geom(shape,shapeType) VALUES('CURVEPOLYGON(CIRCULARSTRING(2 3, 4 1, 6 3, 4 5, 2 3))', 'Circle'), ('POLYGON((1 1, 4 1, 4 5, 1 5, 1 1))', 'Rectangle'); -- Perform UnionAggregate on @Geom.shape column SELECT geometry::UnionAggregate(shape).ToString() FROM @Geom;