Conditions for Casts to GeometryCollection error occurs. If any ring is not in the correct order (exterior ring must be counter-clockwise)  an ER_INVALID_CAST_POLYGON_RING_DIRECTION  error occurs. •If the expression to cast is a well-formed geometry of type  MultiPolygon   the function result is that  MultiPolygon . •If the expression to cast is a well-formed geometry of type  GeometryCollection  containing only polygons  the function result is a  MultiPolygon  containing those polygons. If the expression is empty or contains other geometry types  an  ER_INVALID_CAST_TO_GEOMETRY  error occurs. •If the expression to cast is a well-formed geometry of type other than  Polygon   MultiLineString    MultiPolygon   or  GeometryCollection   an ER_INVALID_CAST_TO_GEOMETRY  error occurs. Conditions for Casts to GeometryCollection • GeometryCollection  and  GeomCollection  are synonyms for the same result type. •If the expression to cast is a well-formed geometry of type  Point   the function result is a GeometryCollection  containing that  Point  as its sole element. •If the expression to cast is a well-formed geometry of type  LineString   the function result is a GeometryCollection  containing that  LineString  as its sole element. •If the expression to cast is a well-formed geometry of type  Polygon   the function result is a GeometryCollection  containing that  Polygon  as its sole element. •If the expression to cast is a well-formed geometry of type  MultiPoint   the function result is a GeometryCollection  containing the points in the order they appear in the expression. •If the expression to cast is a well-formed geometry of type  MultiLineString   the function result is a  GeometryCollection  containing the linestrings in the order they appear in the expression. •If the expression to cast is a well-formed geometry of type  MultiPolygon   the function result is a GeometryCollection  containing the elements of the  MultiPolygon  in the order they appear in the expression. •If the expression to cast is a well-formed geometry of type  GeometryCollection   the function result is that  GeometryCollection . • TIME • UNSIGNED [INTEGER] • YEAR •For a four-digit number in the range 1901-2155 inclusive  or for a string which can be interpreted as a four-digit number in this range  return the corresponding  YEAR  value. Produces a  TIME  value. Produces an unsigned integer value. Produces a  YEAR  value. Added in MySQL 8.0.22. These rules govern conversion to  YEAR : 2245 These conditions apply when the cast result type is  GeometryCollection :