CREATE TABLE HR (
  country text,
  city text,
  department text,
  name text
);

INSERT INTO HR VALUES
  ('DE', 'Berlin', 'Sales', 'Christian'),
  ('DE', 'Berlin', 'Marketing', 'Sandra'),
  ('DE', 'Frankfurt', 'Sales', 'Stefan'),
  ('AT', 'Innsbruck', 'HR', 'Katrin'),
  ('CH', 'Zurich', 'Sales', 'Alexander');

SELECT country, count(*) FROM HR GROUP BY country;
SELECT country, city, count(*) FROM HR GROUP BY country, city;
SELECT department, count(*) FROM HR GROUP BY department;
SELECT country, department, count(*) FROM HR GROUP BY country, department;