1:展示世界的總人口。

SELECT SUM(population) FROM world;

2:列出所有的洲份, 每個只有一次。

SELECT DISTINCT continent FROM world;

3:找出非洲(Africa)的GDP總和。

SELECT SUM(gdp) FROM world WHERE continent = 'Africa';

4:有多少個國傢俱有至少百萬(1000000)的面積。

SELECT COUNT(name) FROM world WHERE area>=1000000;

5:('France','Germany','Spain')（“法國”，“德國”，“西班牙”）的總人口是多少？

SELECT SUM(population) FROM world WHERE name IN ('France','Germany','Spain');

6:For each continent show the continent and number of countries.

SELECT continent,COUNT(name) FROM world GROUP BY continent;

7:For each continent show the continent and number of countries with populations of at least 10 million.

SELECT continent , COUNT(name) FROM world WHERE population >=10000000 GROUP BY continent;

8:List the continents that have a total population of at least 100 million.

SELECT continent FROM world x
WHERE (SELECT SUM(population) FROM world y WHERE y.continent=x.continent)
GROUP BY continent
HAVING SUM(population)>=100000000;

總結

GROUP BY和HAVING功能

HAVING功能可以在GROUP BY排完的結果後進行篩選，如上面的第8例。