DB2 FOR LUW / DB2FORLUW / A10 - DB2

DB2 may return incorrect result when DB2_COMPATIBILITY_VECTOR is 
set to support the OUTER JOIN (+) syntax, and all the conditions 
below are met: 
 
1. WHERE clause contains a predicate with COALESCE function. 
2. The COALESCE function contains a column from the table used 
in the (+) operator. 
3. The column in 2) is defined NOT NULL. 
4. Another predicate AND to the predicate with COALESCE function 
in (1). 
 
For example: 
CREATE TABLE T1(C1 INTEGER, C2 INTEGER NOT NULL); 
CREATE TABLE T2(C1 INTEGER); 
 
INSERT INTO T1 VALUES (1,1); 
INSERT INTO T2 VALUES 1,2; 
 
SELECT T1.C1,T2.C1 FROM T1,T2 WHERE T1.C1 (+) = T2.C1 AND 
COALESCE(T1.C2,1) = 1 AND T2.C1=2; 
 
The correct result should return 1 row. 
 
T1.C1        T2.C1 
-----------  ----------- 
          -            2 
 
This problem is fixed in DB2 Version 9.7 Fix Pack 6.

**************************************************************** 
* USERS AFFECTED:                                              * 
* ALL                                                          * 
**************************************************************** 
* PROBLEM DESCRIPTION:                                         * 
* See Error Description                                        * 
**************************************************************** 
* RECOMMENDATION:                                              * 
* Upgrade to DB2 version 10.1 Fix Pack 1                       * 
****************************************************************

There are two possible workarounds, 
1) Use the ANSI syntax of the OUTER JOIN 
 
The example above can be written as 
SELECT T1.C1,T2.C1 FROM T1 RIGHT OUTER JOIN T2 ON T1.C1=T2.C1 
WHERE COALESCE(T1.C2,1) = 1 AND T2.C1=2; 
 
2) Separate the COALESCE predicate into a subselect after the 
OUTER JOIN (+) operator predicate 
 
The example above can be written as 
SELECT T1C1, T2C1 
FROM (SELECT T1.C1 as T1C1, T1.C2 as T1C2, T2.C1 as T2C1 FROM 
T1,T2 WHERE T1.C1(+) = T2.C1) AS Q 
WHERE COALESCE(T1C2, 1) = 1 AND T2C1=2;

DB2 Version 10.1 Fix Pack 1 for Linux, UNIX, and Windows
 DB2 Version 10.1 Fix Pack 2 for Linux, UNIX, and Windows
 DB2 Version 10.1 Fix Pack 3 for Linux, UNIX, and Windows
 DB2 Version 10.1 Fix Pack 4 for Linux, UNIX, and Windows
 DB2 Version 10.1 Fix Pack 3a for Linux, UNIX, and Windows
 DB2 Version 10.1 Fix Pack 6 for Linux, UNIX, and Windows
 

Upgrade to DB2 version 10.1 Fix Pack 1

not known / see Local fix

Date  - problem reported    :
Date  - problem closed      :
Date  - last modified       :

13.06.2012
07.11.2012
25.09.2013