sqlzoo刷题 - SELECT within SELECT Tutorial

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本文提供了一系列SQL嵌套查询的实际案例，包括列出人口超过俄罗斯的国家、欧洲国家的人均GDP对比英国、查找阿根廷或澳大利亚所在大陆的所有国家等。通过这些实例，读者可以深入理解并掌握嵌套查询在SQL中的应用。

SELECT within SELECT Tutorial
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1.List each country name where the population is larger than that of ‘Russia’.

SELECT name FROM world
WHERE population > (SELECT population FROM world WHERE name = 'Russia');

2.Show the countries in Europe with a per capita GDP greater than ‘United Kingdom’.

SELECT name 
FROM 
(SELECT *, gdp/population AS Per_Capita_GDP
FROM world) t
WHERE t.continent = 'Europe' AND t.Per_Capita_GDP > (SELECT gdp/population 
FROM world WHERE name = 'United Kingdom')

3.List the name and continent of countries in the continents containing either Argentina or Australia. Order by name of the country.

SELECT name,continent
FROM
world
WHERE continent in (SELECT continent FROM world WHERE name in ('Argentina','Australia'))
ORDER BY name

4.Which country has a population that is more than Canada but less than Poland? Show the name and the population.

SELECT name,population
FROM world
WHERE population > (SELECT population FROM world WHERE name = 'Canada')
AND population < (SELECT population FROM world WHERE name = 'Poland')

5.Show the name and the population of each country in Europe. Show the population as a percentage of the population of Germany.

SELECT name,
CONCAT(ROUND(population*100/(SELECT population FROM world WHERE name='Germany')),'%') 
FROM world 
WHERE continent = 'Europe'

6.Which countries have a GDP greater than every country in Europe? [Give the name only.] (Some countries may have NULL gdp values)

SELECT name
FROM world
WHERE gdp > ALL(SELECT gdp FROM world WHERE gdp>0 AND continent='Europe')

7.Find the largest country (by area) in each continent, show the continent, the name and the area:

SELECT continent, name, area FROM world x
WHERE area >= ALL(SELECT area FROM world y WHERE y.continent = x.continent)

8.List each continent and the name of the country that comes first alphabetically.

SELECT continent ,name FROM world x
WHERE name <= ALL(SELECT name FROM world y WHERE y.continent = x.continent)

9.Find the continents where all countries have a population <= 25000000. Then find the names of the countries associated with these continents. Show name, continent and population.
SELECT name, continent, population FROM world WHERE continent in (SELECT continent FROM world GROUP BY continent HAVING MAX(population)<=25000000)

10.Some countries have populations more than three times that of any of their neighbours (in the same continent). Give the countries and continents.

SELECT name,continent FROM world x
WHERE population > ALL(SELECT 3*population FROM world y WHERE y.continent= x.continent AND y.name != x.name)

20181218练习嵌套语句