--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,
region
FROM bbc x
WHERE population >
-- this sub query finds each neighbour (not including itself) and returns the max populations multiplied by 3
(SELECT 3 * MAX(population)
FROM bbc y
WHERE x.region = y.region
AND x.name <> y.name)--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,
region,
population
FROM bbc x
WHERE population < ALL
-- the ALL keyword allows comparison to be made against all the values in a list
-- this sub query finds each country that belongs to a region with populations less than 25 million and returns this as a list
(SELECT population
FROM bbc y
WHERE y.region = x.region
AND population > 25000000)Copyright © 2021 Codeinu
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