正确使用count（*）和group by函数

Question

在sql中你可以使用GROUP BY函数和像国家一样的列吗？ （这将是一个char / varchar）

SELECT country, population, COUNT(*) AS count_cities
FROM list_of_cities
GROUP BY country;

什么是更好的方式来写这个？

Answer 1

SELECT country, SUM(population) AS country_population, COUNT(*) AS count_cities 
FROM list_of_cities 
GROUP BY country;