https://www.hackerrank.com/challenges/average-population-of-each-continent/problem

📔문제

Given the CITY and COUNTRY tables, query the names of all the continents (COUNTRY.Continent) and their respective average city populations (CITY.Population) rounded down to the nearest integer.

Note: CITY.CountryCode and COUNTRY.Code are matching key columns.

The CITY and COUNTRY tables are described as follows:

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🧮분야

• JOIN

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📃SQL 코드

select continent, floor(avg(city.population))
from city inner join country
on city.countrycode=country.code
group by continent;

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📰출력 결과

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📂고찰

city와 country 테이블을 조인해서, 각 continent별 평균 population을 구해서 내림하라고 했다.

그러므로 floor()함수를 사용했다.