GeomCollection(g [, g] ...)
Constructs a GeomCollection value from the geometry arguments.
GeomCollection() returns all the proper geometries contained in the
arguments even if a nonsupported geometry is present.
GeomCollection() with no arguments is permitted as a way to create an
empty geometry. Also, functions such as ST_GeomFromText() that accept
WKT geometry collection arguments understand both OpenGIS
'GEOMETRYCOLLECTION EMPTY' standard syntax and MySQL
'GEOMETRYCOLLECTION()' nonstandard syntax.
GeomCollection() and GeometryCollection() are synonymous, with
GeomCollection() the preferred function.