DB2 8.2 for Linux, FP 10 (also performs the same on DB2 8.2 for Windoes, FP
11).

Using the SAMPLE database, tables EMP and EMLOYEE.

In the followng stored procedure, 2 NULL columns (COMM) are selected into 2
different SP variables and compared for equal. They are both NULL, but do
not compare as equal. When the Not NULL columns (SALARY) are compared, they
do compare as equal.

Is there a reason for this?

Statement terminator is @.

-- SET THE COMMISION TO NULL ON TWO SAMPLE TABLES FOR EMPNO  '000010'

UPDATE EMP SET COMM = NULL WHERE EMPNO = '000010'@
UPDATE EMPLOYEE SET COMM = NULL WHERE EMPNO = '000010'@

--------------------------------------------------
DROP PROCEDURE TEST_SP@

CREATE PROCEDURE TEST_SP
(
OUT EMP_COMM        DECIMAL(9,2),
OUT EMP_SALARY      DECIMAL(9,2),
OUT EMPLOYEE_COMM   DECIMAL(9,2),
OUT EMPLOYEE_SALARY DECIMAL(9,2),
OUT v_ERRMSG_1      VARCHAR(500),
OUT v_ERRMSG_2      VARCHAR(500)
)
SPECIFIC TEST_SP
RESULT SETS 0
MODIFIES SQL DATA
LANGUAGE SQL
BEGIN

---------------------------------------------
-- Declare variables
---------------------------------------------

DECLARE not_found         CONDITION FOR SQLSTATE '02000';
DECLARE at_end            SMALLINT DEFAULT 0;

DECLARE A_EMPNO           CHAR(6);
DECLARE A_EMP_COMM        DECIMAL(9,2);
DECLARE A_EMP_SALARY      DECIMAL(9,2);

DECLARE B_EMPNO           CHAR(6);
DECLARE B_EMPLOYEE_COMM   DECIMAL(9,2);
DECLARE B_EMPLOYEE_SALARY DECIMAL(9,2);

---------------------------------------------
-- Declare exit handlers
---------------------------------------------

DECLARE EXIT HANDLER FOR SQLEXCEPTION
  GET DIAGNOSTICS EXCEPTION 1 v_ERRMSG_1 = MESSAGE_TEXT;

DECLARE CONTINUE HANDLER FOR not_found
  SET at_end = 1;

DECLARE EXIT HANDLER FOR SQLWARNING
  GET DIAGNOSTICS EXCEPTION 1 v_ERRMSG_1 = MESSAGE_TEXT;

---------------------------------------------------------------
-- Begin processing logic
---------------------------------------------------------------

SELECT EMPNO, COMM, SALARY INTO A_EMPNO, A_EMP_COMM, A_EMP_SALARY
FROM DB2INST1.EMP
WHERE EMPNO = '000010';

SELECT EMPNO, COMM, SALARY INTO B_EMPNO, B_EMPLOYEE_COMM, B_EMPLOYEE_SALARY
FROM DB2INST1.EMPLOYEE
WHERE EMPNO = A_EMPNO;

IF A_EMP_COMM = B_EMPLOYEE_COMM THEN
 SET V_ERRMSG_1 = 'NULLS COMPARE AS EQUAL';
ELSE
  SET V_ERRMSG_1 = 'NULLS DO NOT COMPARE AS EQUAL';
END IF;

IF A_EMP_SALARY = B_EMPLOYEE_SALARY THEN
 SET V_ERRMSG_2 = 'NON-NULLS COMPARE AS EQUAL';
ELSE
  SET V_ERRMSG_2 = 'NON-NULLS DO NOT COMPARE AS EQUAL';
END IF;

SET EMP_COMM = A_EMP_COMM;
SET EMP_SALARY = A_EMP_SALARY;

SET EMPLOYEE_COMM = B_EMPLOYEE_COMM;
SET EMPLOYEE_SALARY = B_EMPLOYEE_SALARY;

END@

CALL TEST_SP (?,?,?,?,?,?)@

Value of output parameters
--------------------------
Parameter Name  : EMP_COMM
Parameter Value : -

Parameter Name  : EMP_SALARY
Parameter Value :  52750.00

Parameter Name  : EMPLOYEE_COMM
Parameter Value : -

Parameter Name  : EMPLOYEE_SALARY
Parameter Value :  52750.00

Parameter Name  : V_ERRMSG_1
Parameter Value : NULLS DO NOT COMPARE AS EQUAL

Parameter Name  : V_ERRMSG_2
Parameter Value : NON-NULLS COMPARE AS EQUAL

Return Status = 0