Returns a union or intersection of a group of ST_Geometry objects.
The kind of geometry objects in the ST_Geometry type column returned by the table operator matches the type of geometry objects that were aggregated.
For Intersection operations, "GEOMETRYCOLLECTION EMPTY" is returned if there is no intersection between the objects.
If the Well-Known Binary (WKB) representation of the resulting geometry becomes larger than the maximum size geometry (~16MB), the system reports an error.
Non-Empty geometry collections are not supported, so any union or intersection that results in a collection, as either an intermediate or final result generates an error. Involving one will result in an error.
Valid Data Types
ST_Geometry objects that represent Points, LineStrings, Polygons, MultiPoints, MultiLineStrings, MultiPolygons, and GeometryCollections