Find the employee with the highest salary per department. Output the department name, employee's first name along with the corresponding salary.
Table: employee
-- employee with the highest salary per dept
-- 1. filter columns
-- 2. groupby dept and find the max
-- 3. search two tables where sal and dept matches
select first_name, m.department, sal from
(select department, max(salary) as sal from employee group by department) m,
(select department, first_name, salary from employee) n
where m.department = n.department and
m.sal = n.salary