Use the following ALTER TABLE syntax to create a system-time table by adding a system-time derived period column and the component start and end columns in a single ALTER TABLE statement:
ALTER TABLE table_name ADD PERIOD FOR SYSTEM_TIME ( sys_start, sys_end ) ADD sys_start TIMESTAMP(6) WITH TIME ZONE NOT NULL GENERATED ALWAYS AS ROW START ADD sys_end TIMESTAMP(6) WITH TIME ZONE NOT NULL GENERATED ALWAYS AS ROW END [;] ALTER TABLE table_name ADD SYSTEM VERSIONING [;]
A system-time table is not considered to be a temporal table, and is not afforded any special temporal behaviors until system versioning has been added to the table. Add system versioning to the system-time table using the following syntax in a separate ALTER TABLE statement:
ALTER TABLE table_name ADD SYSTEM VERSIONING [;]
The ALTER TABLE statement components must be in the order shown, with the derived period column defined before the component start and end columns. There is no comma between the ADD clauses in this case.