SQLZOO ANSWERS - SELECT within SELECT Tutorial

1.  List each country name where the population is larger than that of 'Russia'.

SELECT name FROM world

  WHERE population >

     (SELECT population FROM world

      WHERE name='Russia')

2. Show the countries in Europe with a per-capita GDP greater than 'United Kingdom'.

SELECT name FROM world 

    WHERE  gdp/population >

         (SELECT sum(gdp/population) from world 

            WHERE name = 'United Kingdom') 

        AND continent = 'Europe'

3. List the name and continent of countries in the continents containing either Argentina or Australia.                         Order by name of the country.

SELECT name,continent 

FROM world WHERE continent in 

(SELECT continent FROM world 

WHERE name in ('Argentina','Australia'))

ORDER by name

4  Which country has a population that is more than United Kingdom but less than Germany? Show the name and the           population.

SELECT name,population 

FROM world WHERE population > 

(SELECT population FROM world WHERE name = 'United kingdom')

AND population < 

(SELECT population FROM world WHERE name = 'Germany')

5. Germany (population 80 million) has the largest population of the countries in Europe. Austria (population 8.5 million)         has 11% of the population of Germany.Show the name and the population of each country in Europe. Show the             population as a percentage of the population of Germany.

SELECT name, concat(percentage,'%') 

FROM (SELECT name,round(population*100/

(SELECT population FROM world WHERE name = 'Germany'),0) as percentage 

FROM world WHERE continent = 'Europe')a

6.   Which countries have a GDP greater than every country in Europe? [Give the name only.] (Some countries may have     NULL gdp values)

SELECT name 

FROM world 

WHERE gdp > ALL(SELECT gdp 

FROM world 

WHERE continent = 'Europe' 

AND gdp IS NOT NULL )

7.  Find the largest country (by area) in each continent, show the continent, the name and the area:

SELECT continent, name,area FROM world x

      WHERE area >= ALL

            (SELECT area FROM world y

                    WHERE y.continent=x.continent

                          AND area>0)

8.  List each continent and the name of the country that comes first alphabetically.

SELECT continent,name 

FROM world x WHERE x.name = 

( SELECT MIN(y.name) FROM world y 

WHERE x.continent = y.continent)

9.  Find the continents where all countries have a population <= 25000000. Then find the names of the countries associated with these continents. Show name, continent and population.

SELECT name, continent,population 

FROM world x 

WHERE 25000000 >= 

ALL(SELECT population 

FROM world y WHERE x.continent = y.continent)

10.  Some countries have populations more than three times that of all of their neighbours (in the same continent). Give the countries and continents.

SELECT name,continent 

FROM world x 

WHERE x.population> 

ALL(SELECT 3*y.population 

FROM world y 

WHERE x.continent=y.continent 

AND x.name!=y.name)