[HackerRank/SQL] Basic Join - Population Census

Problem. Basic Join - Population Census

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Link.

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

The PADS | HackerRank

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Description.

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

 

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

 

CITY, COUNTRY 테이블을 사용하여 CONTINENT가 'Asia'인 모든 도시의 총 인구를 조회하는 쿼리문을 작성하시오.

 

CITY 테이블

COUNTRY 테이블

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Key Point. 

SUM,

 

JOIN,

 

WHERE,

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My Answer. 

SELECT SUM(C.POPULATION)
FROM CITY C
    JOIN COUNTRY CO
    ON C.COUNTRYCODE = CO.CODE
WHERE CO.CONTINENT = 'Asia'

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References.