Update one of 2 duplicates in an sql server database table

Question

I have got a table that got a column with duplicate values. I would like to update one of a 2 duplicate values so for example row1 = tom and row2 = tom

Answer 1

I had to put the with inside a from since my sql developer didnt like updating a with Copying from the answer from Nithesh

it ended up looking like this:

UPDATE Clients 
SET Column1 = 'a'
WHERE ColumnID IN (select ColumnID from 
 (  
 SELECT
       row_number() OVER(PARTITION BY Column1  ORDER BY Column1 ) AS rno,
       ColumnID FROM Clients
 )
                   where rno=2   
                  )