set flag who have count greater than a specified number

Question

I have a SQL table to store notification and each user need to see latest 5 notification and need to soft delete remaining notifications(as per the request from client).

In the attached image I need to set IsDeleted flag to 1 for each user who have more than 5 notifications(need to sort in descending order of ID and set flag who have count greater than 5)

Answer 1

I think you want:

with toupdate as (
      select n.*,
             row_number() over (partition by username order by id desc) as seqnum
      from notifications n
     )
update toupdate
    set isdeleted = 1
    where seqnum > 5;