cc = load 'countrycodes.txt' using PigStorage(',') as (ccode:chararray, cname:chararray);
 ccity = load 'worldcitiespop.txt' using PigStorage(',') as (ccode:chararray, cityName:chararray, cityFullName:chararray, region:int, population:long, lat:double, long:double);
 filteredCcity = filter ccity by population is not null;
 joinCountry = join cc by ccode, ccity by ccode;
 generateRecords = foreach joinCountry generate cc::cname, ccity::cityName, ccity::population;
 groupByCountry = group generateRecords by cname;
 populationByCountry = foreach groupByCountry generate group, SUM(generateRecords.population);
 
 
