SQL for DELETE duplicate rows

delete from BOARD.BOARD_RESULT_DATA
 where rowid IN ( select rid
                    from (select rowid rid,
                                 row_number() over (partition by
                         ROLL_NO, REGNO, PASS_YEAR, BOARD_NAME
                                   order by rowid) rn
                            from BOARD.BOARD_RESULT_DATA)
                   where rn <> 1);