SELECT CountryCode, SUM(Population) FROM city WHERE CountryCode = 'NLD';

SELECT CountryCode, SUM(Population) AS res FROM city GROUP BY CountryCode ORDER BY res DESC LIMIT 10;

SELECT CountryCode, SUM(Population) AS res FROM city GROUP BY CountryCode HAVING res > 100000000;

SELECT CountryCode, SUM(Population) AS s, COUNT(*) AS c FROM city GROUP BY CountryCode HAVING s > 1000000 AND c > 100;
