For a table that supports transaction time, the temporal qualifier in the transaction-time dimension is CURRENT TRANSACTIONTIME.
All check, primary key, and temporal unique (current, sequenced, nonsequenced) constraints defined on the table are checked only on rows that are open in transaction time.
If either the target table or source table is a temporal table and the MERGE statement does not specify a temporal qualifier, the value of the session valid-time qualifier is used for the temporal table.
If the source row set is specified by a value list, the source is considered nontemporal.
A select subquery or a table specified as a source row set in the merge statement can reference a temporal table. The derived table can result in a temporal or nontemporal table, depending on the temporal qualifier used.
MERGE is not supported on tables that do not have primary indexes and column-partitioned tables.
The UPDATE portion of the MERGE statement follows the rules of the temporal UPDATE statement semantics and the INSERT portion of the MERGE statement follows the rules of the temporal INSERT statement semantics.
DML operations on tables defined with NORMALIZE produce a normalized set of modified rows. Some unmodified rows may be deleted from the target table as a result of the normalization.
When the target table is a normalized temporal table with transaction time, rows that are deleted as a result of the normalization are closed in transaction time.