****************************************************************
TABLE CREATION
****************************************************************
CREATE TABLE nulltable (A INT);

INSERT INTO nulltable VALUES(10);
INSERT INTO nulltable VALUES(20);
INSERT INTO nulltable VALUES(20);
INSERT INTO nulltable VALUES(NULL);
INSERT INTO nulltable VALUES(NULL);
INSERT INTO nulltable VALUES(NULL);
--------
| A    | 
--------
| 10   |
| 20   | 
| 20   |
| NULL | 
| NULL | 
| NULL | 
--------
****************************************************************
****************************************************************
SELECT * FROM nulltable
--------
| A    | 
--------
| 10   |
| 20   | 
| 20   |
| NULL | 
| NULL | 
| NULL | 
--------
----------------------------------------------------
SELECT DISTINCT A FROM nulltable
--------
| A    | 
--------
| 10   |
| 20   |  
| NULL | 
--------
----------------------------------------------------
SELECT A FROM nulltable WHERE A IS NULL
--------
| A    | 
--------
| NULL | 
| NULL | 
| NULL | 
--------
----------------------------------------------------
SELECT A FROM nulltable WHERE A IS NOT NULL
------
| A  | 
------
| 10 |
| 20 |  
| 20 |  
------
----------------------------------------------------
SELECT A FROM nulltable WHERE A > 10
------
| A  | 
------
| 20 |  
| 20 |  
------
----------------------------------------------------
SELECT A FROM nulltable WHERE A > 10 IS UNKNOWN
--------
| A    | 
--------
| NULL | 
| NULL | 
| NULL | 
--------
----------------------------------------------------
SELECT A FROM nulltable WHERE A > 10 IS NOT UNKNOWN
------
| A  | 
------
| 10 | 
| 20 |  
| 20 |  
------







****************************************************************
TABLE CREATION
****************************************************************
CREATE TABLE nulltabletwo (A INT, B VARCHAR(20));

INSERT INTO nulltabletwo VALUES(10, 'hello');
INSERT INTO nulltabletwo VALUES(20, 'hi');
INSERT INTO nulltabletwo VALUES(NULL, NULL);
INSERT INTO nulltabletwo VALUES(NULL, NULL);
INSERT INTO nulltabletwo VALUES(10, NULL);
INSERT INTO nulltabletwo VALUES(10, NULL);
INSERT INTO nulltabletwo VALUES(NULL, 20);
INSERT INTO nulltabletwo VALUES(NULL, 20);
----------------
| A    | B     |
----------------
| 10   | hello |
| 20   | hi    |
| NULL | NULL  | 	
| NULL | NULL  | 	
| 10   | NULL  | 
| 10   | NULL  | 
| NULL | 20    |
| NULL | 20    |
----------------
****************************************************************
****************************************************************
SELECT * FROM nulltabletwo
----------------
| A    | B     |
----------------
| 10   | hello |
| 20   | hi    |
| NULL | NULL  | 	
| NULL | NULL  | 	
| 10   | NULL  | 
| 10   | NULL  | 
| NULL | 20    |
| NULL | 20    |
----------------
----------------------------------------------------
SELECT DISTINCT * FROM nulltabletwo
----------------
| A    | B     |
----------------
| 10   | hello |
| 20   | hi    |
| NULL | NULL  | 	
| 10   | NULL  | 
| NULL | 20    |
----------------