请教高手如何实现如下结果？

Question

test1表数据如下：zjhm    bjhm
-----------------
a        t1
a        t2
a        t3
b        t1 
b        t2
c        s1
c        s2
c        s3
......
如何依照zjhm和bjhm产生一个虚拟的序号，结果如下：
-----------------------
zjhm    bjhm       xh 
a        t1        1
a        t2        2 
a        t3        3
b        t1        1 
b        t2        2
c        s1        1
c        s2        2 
c        s3        3
......

Answer 1

select zjhm，bjhm,
 row_number()over(partition by zjhm order by bjhm)as xh
  from test1 order by zjhm

Answer 2

select zjhm,bjhm,
       row_number()over(partition by zjhm order by bjhm) as xh
from test1 order by zjhm

Answer 3

ROW_NUMBER
功能描述：返回有序组中一行的偏移量，从而可用于按特定标准排序的行号。
SAMPLE：下例返回每个员工再在每个部门中按员工号排序后的顺序号
SQL> conn hr/hr;
Connected to Oracle9i Enterprise Edition Release 9.0.1.1.1 
Connected as hrSQL> 
SQL> SELECT department_id, last_name, employee_id, ROW_NUMBER()
  2  OVER (PARTITION BY department_id ORDER BY employee_id) AS emp_id
  3  FROM employees
  4  WHERE department_id < 50;DEPARTMENT_ID LAST_NAME                 EMPLOYEE_ID     EMP_ID
------------- ------------------------- ----------- ----------
           10 Whalen                            200          1
           20 Hartstein                         201          1
           20 Fay                               202          2
           30 Raphaely                          114          1
           30 Khoo                              115          2
           30 Baida                             116          3
           30 Tobias                            117          4
           30 Himuro                            118          5
           30 Colmenares                        119          6
           40 Mavris                            203          110 rows selected