Show the role code for all employees.
select role_code from employees
Count the number of employees with each role code.
select role_code, count(*) from employees group by role_code
Sort the codes by the count in descending order.
select role_code from employees group by role_code order by count(*) desc
Which of them has the largest number of employees?
select role_code from employees group by role_code order by count(*) desc limit 1