4.5 - Nested SELECT Quiz

-- 1. Select the code that shows the name, region and population of the smallest country in each region
SELECT region, name, population FROM bbc x WHERE population <= ALL (SELECT population FROM bbc y WHERE y.region=x.region AND population>0)

-- 2. Select the code that shows the countries belonging to regions with all populations over 50000
SELECT name,region,population FROM bbc x WHERE 50000 < ALL (SELECT population FROM bbc y WHERE x.region=y.region AND y.population>0)

-- 3. Select the code that shows the countries with a less than a third of the population of the countries around it
SELECT name, region FROM bbc x
 WHERE population < ALL (SELECT population/3 FROM bbc y WHERE y.region = x.region AND y.name != x.name)

-- 4. Select the result that would be obtained from the following code:
SELECT name FROM bbc
 WHERE population >
       (SELECT population
          FROM bbc
         WHERE name='United Kingdom')
   AND region IN
       (SELECT region
          FROM bbc
         WHERE name = 'United Kingdom')

-- 5. Select the code that would show the countries with a greater GDP than any country in Africa (some countries may have NULL gdp values).
SELECT name FROM bbc
 WHERE gdp > (SELECT MAX(gdp) FROM bbc WHERE region = 'Africa')

-- 6. Select the code that shows the countries with population smaller than Russia but bigger than Denmark
SELECT name FROM bbc
 WHERE population < (SELECT population FROM bbc WHERE name='Russia')
   AND population > (SELECT population FROM bbc WHERE name='Denmark')

-- 7. >Select the result that would be obtained from the following code:
SELECT name FROM bbc
 WHERE population > ALL
       (SELECT MAX(population)
          FROM bbc
         WHERE region = 'Europe')
   AND region = 'South Asia'