SQLzoo答案 SUM and COUNT

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.有多少個國家具有至少百萬(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.對於每一個洲份，顯示洲份和國家的數量。

select continent,count(name) from world

group by continent

7.對於每一個洲份，顯示洲份和至少有1000萬人(10,000,000)口國家的數目。

select continent,count(name) from world

where population >=10000000

group by continent

8.列出有至少100百萬(1億)(100,000,000)人口的洲份。

select continent from world

group by continent

having sum(population)>=100000000