SELECT (MAX(Population) - MIN(Population)) AS Diff FROM City;

select max(population)-min(population) from city;

select max(population)-min(population) from city

mySQL

select max(population)-min(population) as w from city

Here is Population Density Difference problem solution - https://www.gyangav.com/2022/11/hackerrank-population-density-difference-problem-solution.html