SELECT C,D FROM YOUR_TABLE  A 
           WHERE ROWID!=(SELECT MAX(ROWID) FROM YOUR_TABLE E
                                 WHERE A.C=E.C AND A.D=E.D);

------解决方案--------------------

假设mgr不重复
SQL code
SELECT job,mgr FROM emp  A 
           WHERE ROWID = (SELECT max(ROWID) FROM emp E where E.mgr=A.mgr);