SUM and COUNT

1.Total world population

SELECT SUM(population)
FROM world

2.List of continents

select distinct continent
from world

3.GDP of Africa

select sum(gdp)
from world
where continent = 'Africa'

4.Count the big countries

select count(name)
from world
where area >= 1000000

5.Baltic states population

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

6.Using GROUP BY and HAVING

select continent,count(name)
from world
group by continent

7.Counting big countries in each continent

select continent,count(name)
from world
where population >= 10000000
group by continent

8.Counting big continents

select continent
from world
group by continent
having sum(population) >= 100000000