SQL Query to change rownum as text changes in Oracle

Question

I'm stuck with a query wherein i need to change rownum or any running serial no. back to its original value as soon as it founds change of text of second column. I'm using Oracle 11g.

For Eg. My Data is

    ________ 
   | EMP_CD |
   |--------| 
   |  D123  |
   |--------| 
   |  D123  | 
   |--------| 
   |  D123  |
   |--------| 
   |  F743  |
   |--------|  
   |  F743  |
   |________|

So Now What I'm expecting is

 _______ ________ 
| SR NO | EMP_CD |
|-------|--------| 
|   1   |  D123  |
|-------|--------| 
|   2   |  D123  | 
|-------|--------| 
|   3   |  D123  |
|-------|--------| 
|   1   |  F743  |
|-------|--------|  
|   2   |  F743  |
|_______|________|

Answer 1

select row_number() over (partition by emp_cd order by null) as sr_no, emp_cd
from   your_table
order by emp_cd, sr_no;

ORDER BY is optional.

Answer 2

You can use the row_number() analytic function:

SELECT ROW_NUMBER() OVER (PARTITION BY emp_cd ORDER BY 1) AS sr_no, emp_cd
FROM   mytable

Answer 3

您可以使用row_number()分析函数