[MySQL/HackerRank] Revising Aggregations - Averages

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

Revising Aggregations - Averages | HackerRank

문제

Query the average population of all cities in CITY where District is California.

Input Format

The CITY table is described as follows: 

Code

SELECT AVG(POPULATION)
FROM CITY
WHERE DISTRICT = 'CALIFORNIA'