[HackerRank] Population Census

https://www.hackerrank.com/challenges/asian-population/problem?isFullScreen=true 

Population Census | HackerRank

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.

Input Format

The CITY and COUNTRY tables are described as follows:

 

 

[My Answer]

SELECT SUM(A.POPULATION) 
FROM CITY A
inner join
COUNTRY B
ON A.COUNTRYCODE = B.CODE 
AND B.CONTINENT = 'Asia';

 

이전 포스트가 weather 문제 다음 문제가 아니였나보다... 그치 갑자기 조인 세개 거는게 이상하긴 했다.. 순서 실수..