다른 조건 배제하고 제시해준 조건으로만 작성했습니다.

MSSQL 기준으로 작성되었으니

구문은 조금 변경하셔야 할거에요.

---쿼리시작---

;with tblA(A컬럼,B컬럼,C컬럼) As
(
      Select '1','A1','01' From tdual Union All
      Select '2','A4','01' From tdual Union All
      Select '3','A3','02' From tdual Union All
      Select '4','A1','02' From tdual Union All
      Select '5','A6','03'
)
      Select a.A컬럼
            ,IsNull(b.B컬럼 + '[중복]',a.B컬럼) As B컬럼
            ,IsNull(c.C컬럼 + '[중복]',a.C컬럼) As C컬럼
        From tblA a
                    Left Outer Join tblA b On a.B컬럼 = b.B컬럼
                                          And a.A컬럼 > b.A컬럼
                    Left Outer Join tblA c On a.C컬럼 = c.C컬럼
                                          And a.A컬럼 > c.A컬럼

---쿼리끝---