When a SELECT or DML statement refers to a temporal table but does not explicitly specify a valid-time qualifier, the system uses the session valid-time qualifier. Similarly, when a SELECT statement refers to a temporal table but does not explicitly specify a transaction-time qualifier, the system uses the session transaction-time qualifier.
The current session temporal qualifier is reported by the Temporal Qualifier field returned by the HELP SESSION statement.
The default temporal session qualifier depends on whether you use the original Teradata implementation of temporal tables and syntax, as described in this document, or the ANSI/ISO-compliant implementation of temporal tables, as described in Teradata Vantage™ - ANSI Temporal Table Support, B035-1186. This default is determined by Temporal Behavior setting in DBS Control, and is set by Teradata personnel in accordance with your use of temporal tables and syntax. For more information on DBS Control, see Teradata Vantage™ - Database Utilities, B035-1102.