How should I calculate the employee's seniority?

Hi,

I have a query where I calculate the seniority of the employee and I want to sort by the highest seniority.

The query works like this if the 'Seniority Reference Date'(paam1.****_attribute_date6) on the person is empty, it works based on the starting date of the job. You can see it in column d1.

Should I use it this way or should I write it with the EXTRACT function?

and if two different employees started in the same year, I want the one who entered first. so i have to subtract day month year from each other