SQL>
SQL> -- Effects of nulls on boolean expressions.
SQL> SET SERVEROUTPUT ON
SQL>
SQL> DECLARE
2 a INTEGER;
3 n INTEGER; -- be our null value.
4 BEGIN
5 -- Assign a value to the variable A, but leave N null.
6 a := 2;
7 -- NOT NULL = NULL
8 IF (NOT (a = n)) IS NULL THEN
9 DBMS_OUTPUT.PUT_LINE('NOT NULL = NULL');
10 END IF;
11 END;
12 /
NOT NULL = NULL
PL/SQL procedure successfully completed.
SQL>