DB2SQL92> CREATE TABLE testtab (
  label VARCHAR(30) NOT NULL PRIMARY KEY,
  a VARCHAR(10),
  b VARCHAR(10)
);DB2SQL92> DB2SQL92> DB2SQL92> DB2SQL92>
 
Statement # 16 :
CREATE TABLE testtab (  label VARCHAR(30) NOT NULL PRIMARY KEY,  a
VARCHAR(10),  b VARCHAR(10)  )
 
Elapsed Time is:           0.020      seconds
 
---------------------------------------------
DB2SQL92> INSERT INTO testtab VALUES('both null',NULL,NULL);
 
Statement # 17 :
INSERT INTO testtab VALUES('both null',NULL,NULL)
 
Elapsed Time is:           0.005      seconds
 
---------------------------------------------
DB2SQL92> INSERT INTO testtab VALUES('a null',NULL,'b not null');
 
Statement # 18 :
INSERT INTO testtab VALUES('a null',NULL,'b not null')
 
Elapsed Time is:           0.004      seconds
 
---------------------------------------------
DB2SQL92> INSERT INTO testtab VALUES('b empty string','a','');
 
Statement # 19 :
INSERT INTO testtab VALUES('b empty string','a','')
 
Elapsed Time is:           0.004      seconds
 
---------------------------------------------
DB2SQL92> INSERT INTO testtab VALUES('a null, b empty string',NULL,'');
 
Statement # 20 :
INSERT INTO testtab VALUES('a null, b empty string',NULL,'')
 
Elapsed Time is:           0.004      seconds
 
---------------------------------------------
DB2SQL92> INSERT INTO testtab VALUES('equal non-empty strings','x','x');
 
Statement # 21 :
INSERT INTO testtab VALUES('equal non-empty strings','x','x')
 
Elapsed Time is:           0.004      seconds
 
---------------------------------------------
DB2SQL92> INSERT INTO testtab VALUES('non-equal non-empty strings','x','y');
 
Statement # 22 :
INSERT INTO testtab VALUES('non-equal non-empty strings','x','y')
 
Elapsed Time is:           0.005      seconds
 
---------------------------------------------
DB2SQL92> SELECT * FROM testtab;
 
Statement # 23 :
SELECT * FROM testtab
 
LABEL                           A           B
--------------------------------------------------------
both null                       -           -
a null                          -           b not null
b empty string                  a
a null, b empty string          -
equal non-empty strings         x           x
non-equal non-empty strings     x           y
 
 
Number of rows retrieved is:        6
Number of rows sent to output is:   6
 
Elapsed Time is:           0.005      seconds
 
---------------------------------------------
DB2SQL92> SELECT * FROM testtab WHERE a=b;
 
Statement # 24 :
SELECT * FROM testtab WHERE a=b
 
LABEL                           A           B
--------------------------------------------------------
equal non-empty strings         x           x
 
 
Number of rows retrieved is:        1
Number of rows sent to output is:   1
 
Elapsed Time is:           0.004      seconds
 
---------------------------------------------
DB2SQL92> SELECT * FROM testtab WHERE a<>b;
 
Statement # 25 :
SELECT * FROM testtab WHERE a<>b
 
LABEL                           A           B
--------------------------------------------------------
b empty string                  a
non-equal non-empty strings     x           y
 
 
Number of rows retrieved is:        2
Number of rows sent to output is:   2
 
Elapsed Time is:           0.005      seconds
 
---------------------------------------------
DB2SQL92> SELECT * FROM testtab WHERE b IS NULL;
 
Statement # 26 :
SELECT * FROM testtab WHERE b IS NULL
 
LABEL                           A           B
--------------------------------------------------------
both null                       -           -
 
 
Number of rows retrieved is:        1
Number of rows sent to output is:   1
 
Elapsed Time is:           0.004      seconds
 
---------------------------------------------
DB2SQL92> SELECT * FROM testtab WHERE b IS NOT NULL;
 
Statement # 27 :
SELECT * FROM testtab WHERE b IS NOT NULL
 
LABEL                           A           B
--------------------------------------------------------
a null                          -           b not null
b empty string                  a
a null, b empty string          -
equal non-empty strings         x           x
non-equal non-empty strings     x           y
 
 
Number of rows retrieved is:        5
Number of rows sent to output is:   5
 
Elapsed Time is:           0.005      seconds