The following table describes the allowed combinations of source and target types when both the source and the target types are Period data types.
| Source Type | Target Type |
|---|---|
| PERIOD(DATE) | PERIOD(DATE) |
| PERIOD(TIMESTAMP[(m)] [WITH TIME ZONE]) | |
| PERIOD(TIME[(n)] [WITH TIME ZONE]) | PERIOD(TIME[(m)] [WITH TIME ZONE]) where m is the target precision, m must be greater than or equal to the source precision n. The default for m is 6. |
| PERIOD(TIMESTAMP[(m )] [WITH TIME ZONE]) where m is the target precision, m must be greater than or equal to the source precision n. The default for m is 6. |
|
| PERIOD(TIMESTAMP[(n)] WITH TIME ZONE) | PERIOD(DATE) |
| PERIOD(TIME[(m)] [WITH TIME ZONE]) where m is the target precision, m must be greater than or equal to the source precision n. The default for m is 6. |
|
| PERIOD(TIMESTAMP[(m)] [WITH TIME ZONE]) where m is the target precision, m must be greater than or equal to the source precision n. The default for m is 6. |