How to eliminate duplicate rows based on column max value in sql?

Question

I have a view which returns duplicate rows having field performance, which can be 1,2,3 or 4. I need to select only rows which is having max performance. How to do this ? Tried this :

View :

results needed as follows :

So basically for each employee number group, I need to fetch what is max calender value and corresponding performance value

Answer 1

You can express

the employee record with the highest performance

as:

there is no record (for this employee) with a higher performance

And that gives:

SELECT * FROM employee e
WHERE NOT EXISTS (
   SELECT *
   FROM employee nx
   WHERE nx.employee_nr = e.employee_number
   AND nx.performance > e.performance
   );