than one Polygon , 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 LineString , Polygon , MultiLineString , MultiPolygon , or GeometryCollection , an ER_INVALID_CAST_TO_GEOMETRY  error occurs. 

## Conditions for Casts to MultiPoint 

These conditions apply when the cast result type is MultiPoint : 

•If the expression to cast is a well-formed geometry of type Point , the function result is a MultiPoint  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 MultiPoint  containing the points of the LineString  in the same order. 

•If the expression to cast is a well-formed geometry of type MultiPoint , the function result is that MultiPoint . 

•If the expression to cast is a well-formed geometry of type GeometryCollection  containing only points, the function result is a MultiPoint  containing those points. If the GeometryCollection 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 Point , LineString , MultiPoint , or GeometryCollection , an ER_INVALID_CAST_TO_GEOMETRY  error occurs. 

## Conditions for Casts to MultiLineString 

These conditions apply when the cast result type is MultiLineString : 

•If the expression to cast is a well-formed geometry of type LineString , the function result is a MultiLineString  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 MultiLineString  containing the outer ring of the Polygon  as its first element and any inner rings as additional elements 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 that MultiLineString . 

•If the expression to cast is a well-formed geometry of type MultiPolygon  containing only polygons without inner rings, the function result is a MultiLineString  containing the polygon rings in the 

