Deleting Duplicate Keys

Code
DELETE duplicate_column FROM TABLE WHERE row_id NOT IN (SELECT max(row_id) FROM TABLE GROUP BY duplicate_column);

delete from where rowid in (select max/min(rowid) from group by having count(*)>1)

Replace select with delete:

Code
SELECT ename FROM emp1 e
 WHERE ROWID > ( SELECT MIN(rowid)
            FROM emp1
            WHERE ename = e.ename)
 
 
SELECT * FROM
   (
    SELECT empno, ename, job
          ,RANK() OVER (PARTITION BY ename, job ORDER BY empno) AS SeqNo
      FROM emp1
    )
 WHERE SeqNo > 1
/
 

Code
SELECT empno FROM  emp WHERE empno NOT IN(SELECT MIN(empno FROM emp GROUP BY empno);

To make my prev. posts readable...

Replace select with delete:

SELECT ename FROM emp1 e WHERE ROWID > (SELECT MIN(rowid) FROM emp1 WHERE ename = e.ename)

Assuming that ename and job is the same or First and Last name...

SELECT * FROM (SELECT empno, ename, job ,RANK() OVER (PARTITION BY ename, job ORDER BY empno) AS SeqNo FROM emp1) WHERE SeqNo > 1

Code
 SQL> DELETE FROM table_name WHERE rowid NOT IN (SELECT max(rowid) FROM TABLE GROUP BY duplicate_values_field_name); 
OR 
SQL> DELETE duplicate_values_field_name dv FROM table_name ta WHERE rowid <(SELECT min(rowid)  FROM table_name tb WHERE ta.dv=tb.dv);