CollectionAggregate (geometry Data Type)
Applies to: 
SQL Server
Azure SQL Database
Azure SQL Managed Instance
Creates a GeometryCollection instance from a set of geometry types.
Syntax
CollectionAggregate ( geometry_operand )
Arguments
geometry_operand
Is a geometry type table column that represents a set of geometry objects to be listed in the GeometryCollection instance.
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 a GeometryCollection instance that contains a CurvePolygon and a Polygon.
-- Setup table variable for CollectionAggregate 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 CollectionAggregate on @Geom.shape column
SELECT geometry::CollectionAggregate(shape).ToString()
FROM @Geom;