複数行あるデータを１列１行内に結合して表示させたい

CREATE TABLE birdfly.TableA
(aCol1 INTEGER NOT NULL
,aCol2 INTEGER NOT NULL
,aCol3 INTEGER NOT NULL
);

INSERT INTO birdfly.TableA
VALUES
 (1,　　1,　　2)
,(2,　　1,　　4)
,(3,　　1,　　1)
,(4,　　2,　　3)
,(5,　　2,　　5)
;

CREATE TABLE birdfly.TableB
(bCol1 SMALLINT    NOT NULL
,bCol2 VARCHAR(10) NOT NULL
);

INSERT INTO birdfly.TableB
VALUES
 (1,  'あああ')
,(2,  'いいい')
,(3,  'ううう')
,(4,  'えええ')
,(5,  'おおお')
;

CREATE TABLE birdfly.TableC
(cCol1 INTEGER    NOT NULL
,cCol2 VARCHAR(5) NOT NULL
);

INSERT INTO birdfly.TableC
VALUES
 (1,  'AAA')
,(2,  'BBB')
,(3,  'CCC')
,(4,  'DDD')
,(5,  'EEE')
;


SELECT CHAR(bCol1)  AS "bCol1"
     , bCol2        AS "xCol2"
     , c1.cCol2
       || COALESCE(', '||c2.cCol2, '')
       || COALESCE(', '||c3.cCol2, '')
                    AS "xCol3"
  FROM birdfly.TableB
       INNER JOIN
       birdfly.TableA a1
       INNER JOIN
       birdfly.TableC c1
         ON  c1.cCol1 = a1.aCol3
         ON  bCol1 = a1.aCol2
       LEFT OUTER JOIN
       birdfly.TableA a2
       INNER JOIN
       birdfly.TableC c2
         ON  c2.cCol1 = a2.aCol3
         ON  bCol1 = a2.aCol2
         AND a2.aCol1 = a1.aCol1 + 1
       LEFT OUTER JOIN
       birdfly.TableA a3
       INNER JOIN
       birdfly.TableC c3
         ON  c3.cCol1 = a3.aCol3
         ON  bCol1 = a3.aCol2
         AND a3.aCol1 = a2.aCol1 + 1
 WHERE a1.aCol1
       = (SELECT MIN(aCol1)
            FROM birdfly.TableA am
           WHERE am.aCol2 = a1.aCol2);
------------------------------------------------------------------------------

bCol1  xCol2      xCol3              
------ ---------- -------------------
1      あああ     BBB, DDD, AAA      
2      いいい     CCC, EEE           

  2 record(s) selected.