[HackerRank] Basic Join : Asian Population

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:

풀이

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