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 -- But also note that the test for a <> n fails.
8 IF a <> n THEN
9 DBMS_OUTPUT.PUT_LINE('a <> n is true');
10 ELSE
11 DBMS_OUTPUT.PUT_LINE('a <> n is not true');
12 END IF;
13
14 END;
15 /
a <> n is not true
PL/SQL procedure successfully completed.
SQL>