How to find 5 largest salary in nth nob of Record

Answer 1

You can use MAX function to return rows with largest salary and using LIMIT. e.g. SELECT MAX(Salary) FROM Customers LIMIT 5;

Answer 2

select max(SALARY) ... returns exactly one row, the maximum salary found in the table respectively.
You better use this statement:
select SALARY from CUSTOMERS order by SALARY desc limit 5;