SQLZoo-SELECT within SELECT Tutorial

List each country name where the population is larger than that of 'Russia'.

sql 复制代码

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

Show the countries in Europe with a per capita GDP greater than 'United Kingdom'.

sql 复制代码

SELECT name FROM world
  WHERE continent = 'Europe' AND gdp/population >
     (SELECT gdp/population FROM world
      WHERE name='United Kingdom')

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

sql 复制代码

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

Which country has a population that is more than United Kingdom but less than Germany? Show the name and the population.

sql 复制代码

SELECT name, population FROM world
  WHERE population > (
        SELECT population FROM world
        WHERE name = 'United Kingdom') AND population < (
        SELECT population FROM world
        WHERE name = 'Germany')

Germany (population 80 million) has the largest population of the countries in Europe. Austria (population 8.5 million) has 11% of the population of Germany.

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

The format should be Name, Percentage for example:

name	percentage
Albania	3%
Andorra	0%
Austria	11%
...	...

sql 复制代码

SELECT name,
 CONCAT(ROUND(100*population/(
      SELECT population FROM world
      WHERE name = 'Germany'),0),'%') AS percentage
  FROM world
  WHERE continent = 'Europe'

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

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SELECT name FROM world
 WHERE gdp > (
      SELECT Max(gdp) FROM world
      WHERE continent = 'Europe')

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

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SELECT continent, name, area FROM world x
  WHERE area >= ALL
    (SELECT area FROM world y
        WHERE y.continent=x.continent
          AND area>0)

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

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SELECT continent, MIN(name) AS first_country
FROM world
GROUP BY continent
ORDER BY continent

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.

sql 复制代码

SELECT name, continent, population
FROM world
WHERE continent IN (
    SELECT continent
    FROM world
    GROUP BY continent
    HAVING MAX(population) <= 25000000)

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

sql 复制代码

SELECT c1.name AS country, c1.continent
FROM world c1
WHERE c1.population > ALL (
    SELECT 3 * c2.population
    FROM world c2
    WHERE c2.continent = c1.continent
      AND c2.name <> c1.name
);