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);
 groupedCity = cogroup cc by ccode, ccity by ccode;
 flattendGroupedCity = foreach groupedCity generate flatten(cc), flatten (ccity);
 filteredGroup = filter flattendGroupedCity by cc::ccode == ccity::ccode;
 
 
