sqlzoo:SELECT within SELECT Tutorial

忘是亡心i 2022-11-20 00:59 132阅读 0赞

> 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')

> 1.  Show the countries in Europe with a per capita GDP greater than ‘United Kingdom’.

SELECT name 
    FROM world
    WHERE continent='Europe'
      AND gdp/population > 
        (SELECT gdp/population FROM world WHERE name='United Kingdom')

> 1.  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='Argentina' OR name='Australia')
    ORDER BY name

> 1.  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')

> 1.  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(ROUND(100*population/(SELECT population FROM world WHERE name='Germany'), 0), '%') AS percenetage
    FROM world
    WHERE continent='Europe'

> 1.  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>(SELECT gdp FROM world WHERE continent='Europe' ORDER BY gdp DESC limit 1)

> 1.  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)

> 1.  List each continent and the name of the country that comes first alphabetically.

SELECT continent, name
    FROM world x
    WHERE x.name=(SELECT y.name FROM world y WHERE x.continent=y.continent ORDER BY y.name limit 1)

> 1.  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 AND population>0)

> 1.  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/3 >= ALL (SELECT population FROM world y WHERE x.continent=y.continent AND y.name != x.name)