This query calculates a cumulative sum of salary per department and ORDER BY start_date.
SELECT dept_id, start_date, name, salary, SUM(salary) OVER (PARTITION BY dept_id ORDER BY start_date ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) FROM emp1 ORDER BY dept_id, start_date;
DepartmentID start_date name salary sum(salary)
-------- ---------- ---- ------ ----- 100 1996-01-01 Anna 18000 18000 100 1997-01-01 Mike 28000 46000 100 1998-01-01 Scott 29000 75000 100 1998-02-01 Antonia 22000 97000 100 1998-03-12 Adam 25000 122000 100 1998-12-01 Amy 18000 140000 200 1998-01-01 Jeff 18000 18000 200 1998-01-20 Tim 29000 47000 200 1998-02-01 Jim 22000 69000 200 1999-01-10 Tom 28000 97000 300 1998-03-12 Sandy 55000 55000 300 1998-12-01 Lisa 38000 93000 300 1999-01-10 Peter 48000 141000