16.20 - Rules For Using a DEFAULT Function As Part of a RESET WHEN Condition - Teradata Vantage NewSQL Engine

Teradata Vantageā„¢ SQL Functions, Expressions, and Predicates

prodname
Teradata Database
Teradata Vantage NewSQL Engine
vrm_release
16.20
category
Programming Reference
featnum
B035-1145-162K
The following rules apply to the use of the DEFAULT function as part of a RESET WHEN condition:
  • You can specify a DEFAULT function with a column name argument within a predicate. The system evaluates the DEFAULT function to the default value of the column specified as its argument. After the system evaluates the DEFAULT function, it treats it like a literal in the predicate.
  • You can specify a DEFAULT function without a column name argument within a predicate only if there is one column specification and one DEFAULT function as the terms on each side of the comparison operator within the expression.
  • Following existing comparison rules, a condition with a DEFAULT function used with comparison operators other than IS [NOT] NULL is unknown if the DEFAULT function evaluates to null.

    A condition other than IS [NOT]NULL with a DEFAULT function compared with a null evaluates to unknown.

IF a DEFAULT function is used with... THEN the comparison is...
IS NULL TRUE if the default is null,

else it is FALSE.

IS NOT NULL FALSE if the default is null,

else it is TRUE.