[HackerRank] Basic Join > Population Census

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:

---

[MySQL Solution 1]

SELECT SUM(CITY.POPULATION) 
FROM CITY, COUNTRY
WHERE CITY.COUNTRYCODE = COUNTRY.CODE AND COUNTRY.CONTINENT = 'Asia';

 

[MySQL Solution 2]

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

 

 

문제 링크:

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