[HackerRank/SQL] Basic Join - Average Population of Each Continent

Problem. Basic Join - Average Population of Each Continent

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Link.

https://www.hackerrank.com/challenges/average-population-of-each-continent/problem?utm_campaign=challenge-recommendation&utm_medium=email&utm_source=7-day-campaign 

Average Population of Each Continent | HackerRank

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Description.

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.

 

CITY, COUNTRY 테이블을 사용하여 모든 CONTINENT의 이름과 CONTINENT 별 평균인구를 조회하는 쿼리문을 작성하시오.

※ 단, 평균인구 소숫점은 버림(rounded down) 처리하시오.

 

CITY 테이블

COUNTRY 테이블

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Key Point. 

AVG,

 

FLOOR,

 

JOIN,

 

GROUP BY,

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My Answer. 

SELECT C.CONTINENT, FLOOR(AVG(CI.POPULATION))
FROM CITY CI
    JOIN COUNTRY C
    ON CI.COUNTRYCODE = C.CODE
GROUP BY C.CONTINENT

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References.