Rules for Using NULL as a Literal - Teradata Database

Rules for Using NULL as a Literal

The literal NULL can be used in the following ways.

As a CAST source operand, for example.

     CAST (NULL AS value)

As a CASE result, for example.

     CASE expression 

      THEN NULL

     END

or

     CASE expression 

      THEN expression

      ELSE NULL 

     END

As an item specifying a null is to be placed in a column on INSERT or UPDATE.

As a default column definition specification, for example.

     DEFAULT NULL

As an explicit SELECT item, for example.

     SELECT NULL

This usage is a Teradata extension to the ANSI/ISO SQL-2008 standard because it does not specify a FROM clause.

As an operand of a function, for example.

     SELECT TYPE(NULL)

This usage is a Teradata extension to the ANSI/ISO SQL-2008 standard because it does not specify a FROM clause.