SQL> SET ECHO ON
SQL> SET SERVEROUTPUT ON
SQL> DECLARE
2 a INTEGER;
3 b BOOLEAN;
4 n INTEGER; --this will be our null value.
5 BEGIN
6 a := 2;
7
8 IF (a = n) OR (a <> n) THEN
9 DBMS_OUTPUT.PUT_LINE('(a = n) or (a <> n) is true');
10 ELSE
11 DBMS_OUTPUT.PUT_LINE('(a = n) or (a <> n) is not true');
12 END IF;
13 END;
14 /
(a = n) or (a <> n) is not true
PL/SQL procedure successfully completed.
SQL>