Demonstrates the effects of NULLs on Boolean expressions : Boolean « PL SQL Data Types « Oracle PL/SQL Tutorial

1. Oracle PL/SQL Tutorial
2. PL SQL Data Types
3. Boolean

SQL> DECLARE
  2     x NUMBER := NULL;
  3  BEGIN
  4     IF x = 2 THEN
  5        DBMS_OUTPUT.PUT_LINE('x contains 2');
  6     ELSE
  7        DBMS_OUTPUT.PUT_LINE('x doesn''t contain 2');
  8     END IF;
  9
 10     IF x <> 2 THEN
 11        DBMS_OUTPUT.PUT_LINE('x doesn''t contain 2');
 12     ELSE
 13        DBMS_OUTPUT.PUT_LINE('x contains 2');
 14     END IF;
 15  END;
 16  /

PL/SQL procedure successfully completed.

SQL>
SQL>