Quiero equivalente a la funcionalidad GROUP_CONCAT de MySql en DB2.

He intentado la función XML Aggrigate de DB2 para la cocaína de murows.

SELECT a.ID,
       substr(xmlserialize(xmlagg(xmltext( concat(',', SPECIALISATION)))as varchar( 1024 )),2),
       substr(xmlserialize(xmlagg(xmltext(concat(',,, BASIC_SKILL2)))as varchar( 1024 )),2),
       substr(xmlserialize(xmlagg(xmltext(concat(',', BASIC_SKILL1)))as varchar( 1024 )),2) 
FROM candidate_resume_data a,candidate_skills_info b,skill_special_master c,skill_master_basic2 d,skill_master_basic1 e      
WHERE e.SKILL_BASIC1_ID = d.SKILL_BASIC1_ID 
      AND b.ID = a.ID    
      AND d.SKILL_BASIC2_ID = c.SKILL_BASIC2_ID 
      AND b.CANDIDATE_SPECIALISATION_ID = c.SKILL_SPECIAL_ID 
GROUP BY a.ID;

Que me da resultado

ID  |    SPECIALISATION |    BASIC_SKILL2           |   BASIC_SKILL1      |
----+---------------------------------------------------------------------+
1   |    Java,C++       |  Development,Development  |   Software,Software |

Pero quiero un valor distinto / único de BASIC_SKILL2, BASIC_SKILL1.

ID  |    SPECIALISATION |    BASIC_SKILL2   |   BASIC_SKILL1   |
----+-------------------+-------------------+------------------+
1   |    Java,C++       |  Development      |   Software       |