NULL Statement

The NULL statement explicitly specifies inaction; it does nothing other than pass control to the next statement. In a construct allowing alternative actions, the NULL statement serves as a placeholder. For more information, see "NULL Statement".

Syntax

Text description of the illustration null_statement.gif

Usage Notes

The NULL statement improves readability by making the meaning and action of conditional statements clear. It tells readers that the associated alternative has not been overlooked, but that indeed no action is necessary.

Each clause in an IF statement must contain at least one executable statement. The NULL statement meets this requirement. So, you can use the NULL statement in clauses that correspond to circumstances in which no action is taken. The NULL statement and Boolean value NULL are unrelated.

Examples

In the following example, the NULL statement emphasizes that only salespeople receive commissions:

IF job_title = 'SALESPERSON' THEN
   compute_commission(emp_id);
ELSE
   NULL;
END IF;

In the next example, the NULL statement shows that no action is taken for unnamed exceptions:

EXCEPTION
   ...
   WHEN OTHERS THEN
      NULL;