SQL ZOO
By: Jen-Li Chen
Tags: Sql

List each country name where the population is larger than that of ‘Russia’.

Table ‘world’ is as below:

world(name, continent, area, population, gdp) 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 gdp/population from world where

name = 'United Kingdom')

and continent = 'Europe'

;

3. Neighbours of Argentina and Australia

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

(select continent from world where name in ('Argentina', 'Australia')) order by name;

4. Between Canada and Poland

Which country has a population that is more than Canada but less than Poland? Show the name and the population.

select name, population from world

where population > (select population from world where name = 'Canada') and population < (select population from world

where name = 'Poland');



5. Percentages of Germany

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.

Decimal places

You can use the function ROUND to remove the decimal places.

Percent symbol %

You can use the function CONCAT to add the percentage symbol.

select name, concat(round(population/(select population from world where name ='Germany')*100,0), '%') as 'Percentages of Germany' from world where continent = 'Europe';

6. Bigger than every country in Europe

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 > 0);



7. Largest in each continent

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 x.continent = y.continent and y.area > 0)

8. First country of each continent (alphabetically)

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

select continent, name from world x

where name <= all(select name from world y

where x.continent = y.continent);



9. Difficult Questions That Utilize Techniques Not Covered In Prior Sections

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 >= (select max(population) from world y

where x.continent = y.continent);

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

select name, continent from world x

where population > all(select 3*population from world y

where x.continent = y.continent and x.name <> y.name)

Link

Reference