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[HackerRank] Basic Join : Average Population of Each Continent 본문

EDA Study/SQL

[HackerRank] Basic Join : Average Population of Each Continent

김현우 2021. 2. 8. 12:23

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.

Input Format

The CITY and COUNTRY tables are described as follows:

풀이

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