This mandatory clause specifies the data type of the parameter value returned by the function. You can specify any valid data type except TD_ANYTYPE, VARIANT_TYPE and TABLE, including UDTs.
The defined return data type is stored as an entry in DBC.TVFields using the name RETURN0[n], where n is a sequentially defined integer used to guarantee the uniqueness of the value. This ensures that user-defined parameter names are not duplicated.