4 SELECT within SELECT.sql

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


--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 = 'Argentina' 
	OR name = 'Australia')
ORDER BY name


--4. Which country has a population that is more than United Kingom but less than Germany? Show the name and the population
SELECT name, population
FROM world
WHERE population BETWEEN 
	(SELECT population 
	FROM world 
	WHERE name = 'United Kingdom') 
AND 
	(SELECT population 
	FROM world 
	WHERE name = 'Germany') 
AND name NOT IN ('United Kingdom', 'Germany')


--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'),0)),'%')
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 AND (area > 0))


--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 x 
WHERE 25000000 >= ALL(SELECT population 
					  FROM world y 
					  WHERE y.continent=x.continent)


--10. Some countries have populations more than three times that of all 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 (x.name <> y.name))