SQLZOO 04

SELECT within SELECT Tutoria

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 continent = 'Europe'
AND gdp/population >
(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 ('South America','Oceania')
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/(SELECT population 
FROM world WHERE name = 'Germany')*100,0),'%')
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 > (SELECT MAX(gdp) 
FROM world WHERE 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
WHERE area IN
(SELECT MAX(area) FROM world GROUP BY continent);

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

SELECT continent,MIN(name)
FROM world
GROUP BY continent
ORDER BY 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 x.population/3 > ALL
(SELECT population FROM world y
WHERE x.continent=y.continent 
AND x.name != y.name 
AND y.population>0)