Использование IIF
select sum(sales) as sales_sum, IIF(region='Europe','EU', IIF(region='North America','NA',region)) as Region_name
from Sales_2019
group by region
Использование переключателя
SELECT
sum(Sales) as sales_sum,
SWITCH(
Region="Europe", "EU",
Region="North America", "NA"
) AS Region_name
FROM Sales_2019
group by region