5_solutions.sql

--1. Show the total population of the world.

SELECT SUM(population)
FROM world;

--2. List all the continents - just once each.

SELECT DISTINCT continent FROM world;

--3. Give the total GDP of Africa
SELECT SUM(gdp) FROM world WHERE continent = 'Africa';

--4. How many countries have an area of at least 1000000
SELECT COUNT(*) FROM world WHERE area >= 1000000;

--5. What is the total population of ('France','Germany','Spain')

SELECT SUM(population) FROM world WHERE name IN ('France','Germany','Spain');

--6. For each continent show the continent and number of countries.

SELECT continent, COUNT(*) FROM world GROUP BY continent;

--7. For each continent show the continent and number of countries with populations of at least 10 million.

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

--8. List the continents that have a total population of at least 100 million.

SELECT continent FROM world x WHERE (SELECT SUM(population) FROM world y WHERE x.continent = y.continent) >= 100000000 GROUP BY continent;