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

Try this mate

UPDATE Table1 
SET Column1 = column1 +'a'   
WHERE exists(
        select row 
        from (
            SELECT 
                Column1 , 
                Row_Number() over(Partition by Column1 order by Column1) as row 
            FROM Clients
        ) as subquery 
        where subquery.row = 2
    )