Write a query using GROUPING SETS / ROLLUP.

Short answer: ROLLUP creates subtotals and a grand total. GROUPING SETS lists exact aggregation levels. GROUPING(col) detects total rows (NULLs that mean “all”).

Sample solution

SELECT DepartmentId, JobTitle, SUM(Salary) AS TotalSalary
FROM Employees
GROUP BY ROLLUP (DepartmentId, JobTitle);

Use GROUPING() to distinguish real NULL dimension values from rollup NULLs.