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(name) from world
where area > 1000000;

5. What is the total population of (‘Estonia’, ‘Latvia’, ‘Lithuania’)

select sum(population) from world 
where name in('Estonia', 'Latvia', 'Lithuania');

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

select continent,count(name) 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(name) 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
group by continent
having sum(population) >= 100000000;