If you specify a method as the MAP routine for an ordering, it must obey the following rules:
- It must be associated with the UDT for which this ordering is defined.
- Its declared parameter list must be empty.
- Its result data type must be a predefined data type.
Its predefined data type is valid except the following:
- It must be declared to be DETERMINISTIC.
- The name you specify for it in the ordering definition must be the name of a method contained within the SYSUDTLIB database.
- If you create a structured UDT that might be used for a hash index definition, you must ensure that its ordering function never returns a null. If it does, Teradata Database returns an error to the requestor.
See CREATE METHOD for details about method associations with UDTs, parameters, result data types, and the DETERMINISTIC option.