Oracle rewrite query using rank or dense_rank - oracle

Question

I have the following query and sample data, which is working fine. It finds the max salary for employee(s) for each department.
Although it works, I like to change it to use rank or dense_rank (unsure how to do this) to achieve the output I GENERATED below but
Note department_id=1 has 2 different employees making the exact salary and I need to keep the result like that. In addition, is there a way I can only compare e.department_id = d.department_id once?
Any help would be greatly appreciated. Below is my test CASE and sample data.
CREATE table dept (department_id, department_name) AS
SELECT 1, 'IT' FROM DUAL UNION ALL
SELECT 2, 'SALES' FROM DUAL;
CREATE TABLE employees (employee_id, manager_id, first_name, last_name, department_id, sal,
serial_number) AS
SELECT 1, NULL, 'Alice', 'Abbot', 1, 100000, 'D123' FROM DUAL UNION ALL
SELECT 2, 1, 'Beryl', 'Baron',1, 50000,'D124' FROM DUAL UNION ALL
SELECT 3, 1, 'Carol', 'Chang',1, 100000, 'A1424' FROM DUAL UNION ALL
SELECT 4, 2, 'Debra', 'Dunbar',1, 75000, 'A1425' FROM DUAL UNION ALL
SELECT 5, NULL, 'Emily', 'Eden',2, 90000, 'C1725' FROM DUAL UNION ALL
SELECT 6, 3, 'Fiona', 'Finn',1, 88500,'C1726' FROM DUAL UNION ALL
SELECT 7,5, 'Grace', 'Gelfenbein',2, 55000, 'C1727' FROM DUAL;
select
e.employee_id,
e.first_name,
e.last_name,
e.department_id,
d.department_name,
e.sal
from employees e join dept d on e.department_id = d.department_id
where not exists
( select null
from employees
where department_id = e.department_id
and sal > e.sal );
EMPLOYEE_ID FIRST_NAME LAST_NAME DEPARTMENT_ID DEPARTMENT_NAME SAL
1 Alice Abbot 1 IT 100000
3 Carol Chang 1 IT 100000
5 Emily Eden 2 SALES 90000

Answer 1

You may use RANK as follows:
WITH cte AS (
SELECT e.employee_id, e.first_name, e.last_name, e.department_id,
d.department_name, e.sal,
RANK() OVER (PARTITION BY e.department_id ORDER BY e.sal DESC) rnk
FROM employees e
INNER JOIN dept d ON e.department_id = d.department_id
)
SELECT employee_id, first_name, last_name, department_id, department_name, sal
FROM cte
WHERE rnk = 1;