[MSSQL] 해커랭크(HackerRank) - Revising Aggregations - Averages

https://www.hackerrank.com/challenges/revising-aggregations-the-average-function/problem?isFullScreen=true

문제

해석
district 값이 california 인 모든 도시의 평균 인구를 쿼리합니다.

select
    avg(population)
from
    city
where
    district = 'california'