--举例如下
SQL> delete emp
  2      where not exists (select 1 from
  3          (select rownum rn,empno from emp) t
  4          where t.empno=emp.empno and t.rn in(2,5));

已删除12行。

SQL> select * from emp;

     EMPNO ENAME                JOB                       MGR HIREDATE          
---------- -------------------- ------------------ ---------- --------------    
       SAL       COMM     DEPTNO                                                
---------- ---------- ----------                                                
      7499 Allen                SALESMAN                 7698 20-2月 -81        
      1600        300         30                                                
                                                                                
      7654 Martin               SALESMAN                 7698 28-9月 -81        
      1250       1400         30                                                
                                                                                

SQL> rollback;

回退已完成。

------解决方案--------------------
delete emp
      where not exists (select 1 from
          (select rownum rn,empno from emp) t
          where t.empno=emp.empno and t.rn in(2,5));