SQLZOO ANSWERS - 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 

            (SELECT continent,SUM(population) pop 

                    FROM world GROUP BY continent)a

        where a.pop>=100000000