Fetch data using group by but last updated record

I want to display records on the basis of last updated , if updated column is empty then create date

It should print:-

If data is like below:-

It should print:-

I am writing below query but unable to fetch the same it everytime fetches the second thing even though I have updatedate present

     select Id,at.SubjectId,at.marksid 
from student at 
INNER JOIN (
      select MAX(Id) as StudentId from student  
       group by SubjectId,marksid
      ORDER BY COALESCE(UPDATEDATE,ENTRYDATE) desc 
      ) maxat ON at.Id=maxat.StudentId
        

Further info.

MySQL version 8.0

Entry date cant be null it will have data, Kind of auto generated when data inserts to this table

Please include all the details in the question so it could help future readers as well.

As per the question using row_number is one option.

select Id,
       SubjectId,
       MarksId,
       Entrydate,
       UpdatedDate
from (  select *,
               row_number() over(partition by SubjectId,MarksId order by (case when UpdatedDate is null then Entrydate else Entrydate  end) desc) as rn
        from student
     ) tbl
where rn=1; 

https://dbfiddle.uk/di517ZLv