DENSE_RANK() with two order by columns with the same value

I'm trying to rank a list of payments using DENSE_RANK() function and ordering the results by two data points [PAYROLL DATE] and [PROCESS DATE]. However, when the two columns in the ORDER BY are the same, the DENSE_RANK() is treating them as the same rank.

Here is a snippet of what my query says.

DENSE_RANK() OVER (PARTITION BY [Plan ID], [EE ID], [Loan Number] 
                   ORDER BY ISNULL([PAYROLL DATE], [PROCESS DATE]) ASC)

In the above example, I want the ranking to go from 1 to 4. What I am seeing is that all three records with dates of 2/18 are being lump together (all ranked as 3). Is there another function I should use to get the results I want?

Thank you in advance!

I've tried different variations of DENSE_RANK() to no avail. I've also tried RANK() and ROW_NUMBER() and nothing is truly giving me what I'm looking for in the results.

One way to using a case expression in your order by clause to manage those null values.

create table table1 (
  plan_id varchar(10), 
  ee_id integer, 
  loan_number integer, 
  payroll_date date, 
  process_date date);

insert into table1 values 
('aaa', 1234, 1, '2021-11-26', null), 
('aaa', 1234, 1, '2021-12-23', null), 
('aaa', 1234, 1, '2022-02-18', null), 
('aaa', 1234, 1, '2022-02-18', null), 
('aaa', 1234, 1, null, '2022-02-18'); 

select plan_id, ee_id, loan_number, payroll_date, process_date, 
 DENSE_RANK() OVER 
  (PARTITION BY plan_id,ee_id,loan_number ORDER BY case when payroll_date is null then 1 else 0 end, payroll_date,process_date asc) as r  
from table1

fiddle

EDIT

Or, continue using your ISNULL expression but use a far-fetched future date instead of the process_date. HOWEVER, this alternate answer may not provide desired results if you have more than one null payroll_date row with the same partitioned_by columns, but different process_dates. This works fine if null appears just once. Therefore, I would probably stick with the case expression answer.

select plan_id, ee_id, loan_number, payroll_date, process_date, 
 dense_RANK() OVER 
  (PARTITION BY plan_id,ee_id,loan_number ORDER BY isnull(payroll_date,'9999-12-31') asc) as r  
from table1