【SQL練習】【SQLZOO】 5 SUM and COUNT

5 SUM and COUNT

問題はこちらです。
SUM and COUNT/ja - SQLZOO

以下が解答となります。

1.世界人口のトータル

【解答】

SELECT SUM(population) AS 'total population' FROM world;

2.大陸のリスト

【解答】

SELECT DISTINCT continent FROM world;

3.アフリカのGDP

【解答】

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

4.大きな国の数

【解答】

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

5.バルト三国の人口

【解答】

SELECT SUM(population) AS 'total population'
FROM world WHERE name IN ('Estonia', 'Latvia', 'Lithuania'); 

6.各大陸の国の数を数える

【解答】

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

7.各大陸の大きな国を数える

【解答】

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

8.大きな大陸を数える

【解答】

SELECT continent
FROM world GROUP BY continent 
HAVING SUM(population) >= 100000000;