SQL combined SELECT statement
SELECT name, continent, population
FROM world w
WHERE NOT EXISTS ( -- there are no countries
SELECT *
FROM world nx
WHERE nx.continent = w.continent -- on the same continent
AND nx.population > 25000000 -- with more than 25M population
);
SELECT name, continent, population
FROM world x
WHERE 25000000 > ALL(SELECT population
FROM world y
WHERE y.continent = x.continent
)
The 'ALL'
part compares the population of all the countries in a continent with 25000000 and if it less than 25000000, it prints names, population of all countries in it.
The following code worked for me:
SELECT name, continent, population FROM world x
WHERE 25000000>=ALL (SELECT population FROM world y
WHERE x.continent=y.continent
AND population>0)