Combining Multiple Rows Based Off Criteria

Hello again,

Another combining multiple rows teaser, during a few routines I made a mistake and I would like to combine my efforts. Here is my data:


Code:


Table A

ID DSN VN AX Diag
1111296.54
3212318.00



Both DSNs share the same Patient_id in a seperate table which holds the DSN numbers and their corresponding patients.


Code:


Table B

DSN Patient_id
100000001
200000001



So what I need to do is maintain their unique 'ID' number in Table A but update their DSN numbers to reflect the first instance in Table B. So my data would look like this in both tables.


Code:


Table A

ID DSN VN AX Diag
1111296.54
3112318.00

Note: The second rows DSN changed to 1 from 2




Code:


Table B

DSN Patient_id
100000001
(Duplicate row removed with same patient_id)



The result would look like the above but as you noticed I need to remove the duplicate row that had the different DSN in Table B so that only one DSN remains that can map to multiple rows (IDs) in Table A.

Table A:

DSN can map to multiple rows (IDs)
IDs must be unique (aka kept to what they are currently)

Table B:

Second row with same DSN must be removed.

Any takes, ideas? I need to do this on a couple thousand rows....

Thanks, and im happy to clarify if needed.