05-sum_and_count.sql

-- Show the total population of the world.
SELECT SUM(population)
FROM world

-- List all the continents - just once each.
SELECT distinct continent
FROM world

-- Give the total GDP of Africa
SELECT sum(gdp) 
FROM world 
WHERE continent = 'Africa'

-- How many countries have an area of at least 1000000
SELECT COUNT(name)
FROM world
where area > 1000000

-- What is the total population of ('Estonia', 'Latvia', 'Lithuania')
SELECT SUM(population)
FROM world
WHERE name in ('Estonia', 'Latvia', 'Lithuania')

-- For each continent show the continent and number of countries.
SELECT continent, COUNT(name)
FROM world
GROUP BY continent

-- 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

-- List the continents that have a total population of at least 100 million.
SELECT continent
FROM world
GROUP BY continent
HAVING SUM(population) >= 100000000