UNTIL_CLOSED and UNTIL_CHANGED are special terms that are understood by Teradata Database under some circumstances to represent the ending bound of temporal time periods when the duration is indefinite, forever, or for which the end is an unspecified and unknown time in the future. The terms represent “the maximum system timestamp or date value.”
Although these terms do not conform to current ANSI standards, Teradata Database supports the use of UNTIL_CHANGED for INSERTs and some queries of ANSI valid-time tables.
These four functions, also extensions to the ANSI standard, can be used in WHERE clauses when querying ANSI temporal tables in Teradata Database:
For more information on these functions, see SQL Functions, Operators, Expressions, and Predicates, and the discussion of Period data types in SQL Data Types and Literals.