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

update wmwhse1.sku
set descr= concat (descr,'.')
where exists
(select SKU,count (DESCR)
from wmwhse1.sku
group by descr
having (count (DESCR)>1))

all sku description is updating when I run this script.

output: only 1 row should be affected