WITH
 T1(AAA,ANAME) AS (VALUES
('001','aaa'),
('002','bbb'),
('003','ccc'))
,T2(AAA,BBB,BNAME) AS (VALUES
('001','011','가가가'),
('001','012','나나나'),
('002','021','다다다'),
('003','031','라라라'))

----------------

   SELECT  *
     FROM  (
       SELECT  DISTINCT AAA KEY ,GUB
              ,CASE WHEN GUB = '1' THEN AAA   ELSE BBB   END CODE 
              ,CASE WHEN GUB = '1' THEN ANAME ELSE BNAME END NAME
         FROM (
           SELECT  T1.AAA AAA ,T1.ANAME ANAME
                  ,T2.BBB BBB ,T2.BNAME BNAME
             FROM  T1 ,T2
            WHERE  T1.AAA = T2.AAA
           ) R1
           ,(
           SELECT  '1'  GUB  FROM  SYSIBM.SYSDUMMY1  UNION ALL
           SELECT  '2'  GUB  FROM  SYSIBM.SYSDUMMY1
           ) DUAL
       ) AA
 ORDER BY  KEY ,GUB ,CODE
  
KEY GUB CODE NAME  
--- --- ---- ------
001 1   001  aaa   
001 2   011  가가가
001 2   012  나나나
002 1   002  bbb   
002 2   021  다다다
003 1   003  ccc   
003 2   031  라라라