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 -- TRUE and NULL = NULL
8 IF (a = 2) AND (a <> n) THEN
9 DBMS_OUTPUT.PUT_LINE('TRUE and NULL = TRUE');
10 ELSE
11 DBMS_OUTPUT.PUT_LINE('TRUE and NULL = NULL');
12 END IF;
13 END;
14 /
TRUE and NULL = NULL
PL/SQL procedure successfully completed.
SQL>