[HackerRank][SQL][JOIN] Basic Join, Population Census - 컴도리돌이

Population Census | HackerRank

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Problem

 

 

Given the CITY and COUNTRY tables, query the sum of the populations of all cities where the CONTINENT is 'Asia'.

-> 아시아에 있는 모든 도시의 인구 수의 합을 출력하시오.

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Answer

select sum(a.population)
from city a inner join country b on a.countrycode = b.code
where b.continent = "Asia"