Full Outer Join

  Continent  Export    Country   Continent  Export    Country
  ------------------------------------------------------------
  AFR        oil       Egypt                                  
                                 ASIA       rice      Vietnam 
  EUR        rice      Italy     EUR        beets     Belgium 
  EUR        rice      Italy     EUR        corn      Spain   
  EUR        corn      France    EUR        beets     Belgium 
  EUR        corn      France    EUR        corn      Spain   
  NA         wheat     Canada    NA         sugar     USA