Same Row_Number for Same Values

Question

I need to have row numbering where the ROW_NUMBER is the same for same value column: MFGPN (Same MFGPN will always be in sequence). I also need to maintain the original sequence by No.

Here's my table

No     MFGPN
1      Z363700Z01
2      Z363700Z01
3      0119-960-1
4      1A3F1-0503-01

I tried using RANK() to achieve the desired but am running into trouble.

SELECT RANK() OVER(ORDER BY MFGPN) As [Item], MFGPN FROM Table1 ORDER BY [No] ASC

RESULT

Item   MFGPN           Desired Result
3      Z363700Z01            1
3      Z363700Z01            1
1      0119-960-1            2
2      1A3F1-0503-01         3

Appreciate you guys' expert advise. Thanks!

Answer 1

Use DENSE_RANK window function instead of RANK. Rank will skip the sequence when there is a repetition of data Dense_Rank will not.

SELECT MFGPN,
        Dense_rank()OVER(ORDER BY m_no) as [Desired Result]
FROM   (SELECT no,
                MFGPN,
                Min(no)OVER(partition BY MFGPN) AS m_no
        FROM   (VALUES (1,'Z363700Z01' ),
                        (2,'Z363700Z01' ),
                        (3,'0119-960-1' ),
                        (4,'1A3F1-0503-01')) tc (no, MFGPN))a 

If no is not unique then change DENSE_RANK to

Dense_rank()OVER(ORDER BY m_no,MFGPN)

Result :

+---------------+----------------+
|     MFGPN     | Desired Result |
+---------------+----------------+
| Z363700Z01    |              1 |
| Z363700Z01    |              1 |
| 0119-960-1    |              2 |
| 1A3F1-0503-01 |              3 |
+---------------+----------------+