Oracle Dublicate Rows

DELETE FROM

   theory_attendance_stage A
WHERE
  a.rowid >
   ANY (
     SELECT
        B.rowid
     FROM
        theory_attendance_stage B
     WHERE
        A.regno = B.regno
    and a.paper_name = b.paper_name );



SELECT
        b.bill_no,b.regno,b.bill_date,b.sem,b.particulars,b.amount,B.rowid
     FROM
       tb_billing B, tb_billing a
     WHERE
     a.rowid > b.rowid and
        A.bill_no = B.bill_no
        order by bill_no