The previous examples show three different load statements that will be performed in an optimized way. Any other operation will render the load non-optimized as shown here:

Non-Optimized:
LOAD 
     City       AS   Cities,
     Country    AS   Countries,
     pick(match(Country, 'United States','United Kingdom','Germany'), 'US', 'GB', 'DE) AS CountryCodes
FROM 'LIB://myConnection/CitiesCountries.qvd'
Where Exists(City);

In this example, I create an extra field matching three countries to their country ISO codes. This will make the load non-optimized.