text: /*
  UNION can also be used to determine all occurrences of a field across multiple tables. Try out this exercise with no starter code.
  */
  
  /*
  Instructions
  Determine all (non-duplicated) country codes in either the cities or the currencies table. The result should be a table with only one field called country_code.
  Sort by country_code in alphabetical order.
  */
  
  SELECT country_code
  FROM cities
  UNION
  SELECT code as country_code
  FROM currencies
  ORDER BY country_code