Oracle NULL IS NULL

NULLNoGreater than/less than/equal to/not equal to any value (including NULL itself), with only: NULL IS NULL

1. SQL>SetServeroutput on
2. SQL>
3. SQL> BEGIN
4. 2 IF (2> NULL)
5. 3 THEN
6. 4 dbms_output.put_line ('>');
7. 5 ELSIF (2 <NULL)
8. 6 THEN
9. 7 dbms_output.put_line ('<');
10. 8 ELSIF (2 = NULL)
11. 9 THEN
12. 10 dbms_output.put_line ('=');
13. 11 ELSIF (2! = NULL)
14. 12 THEN
15. 13 dbms_output.put_line ('! =');
16. 14 ELSE
17. 15 dbms_output.put_line ('Unknown! ');
18. 16 end if;
19. 17
20. 18 IF (NULL = NULL)
21. 19 THEN
22. 20 dbms_output.put_line ('Null = null');
23. 21 ELSIF (NULL! = NULL)
24. 22 THEN
25. 23 dbms_output.put_line ('Null! = Null');
26. 24 ELSIF (null is null)
27. 25 THEN
28. 26 dbms_output.put_line ('Null IS null');
29. 27 ELSE
30. 28 dbms_output.put_line ('Unknown !! ');
31. 29 end if;
32. 30 END;
33. 31/
35. Unknown!
36. NULL IS NULL
38. PL/SQL procedure successfully completed
40. SQL>