[HackerRank/Basic Join] Population Census

https://www.hackerrank.com/challenges/asian-population/problem 

Population Census | HackerRank

 

문제

 

풀이

 

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

 

 

INNER JOIN

 

SELECT <select_list> FROM TABLE A A

INNER JOIN TABLE B B

ON A.Key = B.Key

WHERE <select_condition>