Sum_and_Count.sql

-- SUM and COUNT

-- 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;