The DEFAULT function returns the default value of a column. It has two forms: one that specifies a column name and one that omits the column name. Predicates support both forms of the DEFAULT function, but the following conditions must be true when the DEFAULT function omits the column name:
- The predicate uses a comparison operator
- The comparison involves a single column reference
- The DEFAULT function is not part of an expression
For example, the following statement uses DEFAULT to compare the values of the Dept_No column with the default value of the Dept_No column. Because the comparison operation involves a single column reference, Teradata Database can derive the column context of the DEFAULT function even though the column name is omitted.
SELECT * FROM Employee WHERE Dept_No < DEFAULT;
Note that if the DEFAULT function evaluates to null, the predicate is unknown and the WHERE condition is false.