16.20 - Rules For Using a DEFAULT Function As Part of a RESET WHEN Condition - Advanced SQL Engine - Teradata Database

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.