SELECT SUM(CITY.POPULATION) FROM CITY JOIN COUNTRY ON CITY.CountryCode = COUNTRY.Code WHERE CONTINENT = 'Asia';

select sum(city.population) from city join country on city.countrycode = country.code where continent = "Asia"

select sum(c.population) from city c join country cn on c.CountryCode = cn.Code where cn.continent='Asia';

I am just trying out LIKE in this code snippet

SELECT SUM(city.population) FROM city INNER JOIN country ON city.countrycode = country.code WHERE country.continent LIKE '%sia';

SELECT SUM(POPULATION)
FROM CITY
WHERE COUNTRYCODE IN (
    SELECT CODE
    FROM COUNTRY
    WHERE CONTINENT = 'Asia')

we can use the Where statement to match the Country code keys