DB2 FOR LUW / DB2FORLUW / A10 - DB2

Queries containing UNION or UNION ALL operators with "LIMIT # 
OFFSET #" clause does not behave the same way as FETCH FIRST N 
ROWS ONLY. As such, under these conditions, it may return more 
rows than expected. 
 
Consider a query using the "FETCH FIRST 1 ROW ONLY" clause : 
> select 1 C1 from sysibm.sysdummy1 
  union all 
   select 2 C1 from sysibm.sysdummy1 
   ORDER BY C1 ASC 
   FETCH FIRST 1 ROWS ONLY 
 
Which returns: 
C1 
 
          1 
 
  1 record(s) selected. 
 
 
Using the same data with a "LIMIT 1 OFFSET 0" clause to mimic 
the "FETCH FIRST 1 ROWS ONLY" 
> select 1 C1 from sysibm.sysdummy1 
   union all 
   select 2 C1 from sysibm.sysdummy1 
   ORDER BY C1 ASC 
   LIMIT 1 OFFSET 0 
 
We get more rows than expected if this is used in conjunction 
with UNION or UNION ALL: 
 
C1 
 
          1 
          2 
 
  2 record(s) selected. 
 
> select 1 C1 from sysibm.sysdummy1 
   union all 
   select 2 C1 from sysibm.sysdummy1 
   ORDER BY C1 ASC 
   LIMIT 1 OFFSET 1 
 
C1 
 
          1 
          2 
 
  2 record(s) selected. 
 
 
The problem can be circumvented as follows : 
 
> select * from 
     ( select 1 C1 from sysibm.sysdummy1 
       union all 
       select 2 C1 from sysibm.sysdummy1 
       ORDER BY C1 ASC ) 
    LIMIT 1 OFFSET 0 
 
C1 
 
          1 
 
  1 record(s) selected.

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* USERS AFFECTED:                                              * 
* all                                                          * 
**************************************************************** 
* PROBLEM DESCRIPTION:                                         * 
* See Error Description                                        * 
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* RECOMMENDATION:                                              * 
* Upgrade to version 10.1 Fix Pack 5                           * 
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First fixed in version 10.1 Fix Pack 5

not known / see Local fix

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

18.09.2014
16.07.2015
16.07.2015