I am going over a past paper for a database course I am taking and I am stuck on an SQL question
Here is the schema provided
Country(name, capital, area), name is the key
People(country, population, children, adult) where country refers to the name in Country, population is the total population, and children and adult is the percentage of the children and adult population.
Language(country,language,percentage) – for each language spoken in the country, it lists the percentage of the population that speaks the language.
Here is the question:
Write the following query in SQL: Find languages that are only spoken in countries whose total population exceeds 10^7.
This is what I have so far:
SELECT l.language
FROM people p, language l
WHERE l.country = p.country AND
p.population > 10^7
The bit I am confused about is how to check that there are no other countries which a language is spoken in but the population is less than 10^7.
Any advice? Thanks