sqlzool练习--SELECT and COUNT

1.Show the total population of the world.

SELECT SUM(population)
  FROM world

2.List all the continents - just once each.

SELECT continent
  FROM world
GROUP BY continent

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 ('France','Germany','Spain')