proc sort data=sashelp.zipcode out=ByCity;
  where StateName="Delaware" and CountyNm="Kent";
  by City;
run;
data primary dups;
  set ByCity;
  by City;
  if first.City then output primary;
  else output dups;
run;
proc print data=primary noobs;
  var City ZIP;
  title1 "Primary ZIP Codes in Kent County, Delaware";
run;
proc print data=dups;
  by City;
id City;
  var ZIP;
  title1 "Additional ZIP Codes for Kent County, Delaware Cities";
run;