Final answer:
The SQL query calculates the sum of the product of stock dividends and exchange rates for each nation code, with one sum per unique nation code.
Step-by-step explanation:
The result of the SQL query SELECT SUM(stock.stockdiv * nation.exchrate) FROM stock JOIN nation ON stock.natcode = nation.natcode GROUP BY nation.natcode; would be a dataset with the combined total of each stock's dividend (stockdiv) multiplied by the exchange rate (exchrate) for each unique nation code (nation.natcode). This calculation is done for each group of stocks associated with the same nation code because the GROUP BY clause is used. So, for each nation represented in the stock table, you would get a sum of the product of that nation's stocks' dividends and exchange rates.
Note that if there are any null values in either column used in the multiplication, the entire product for that row will be considered null and not counted in the sum for that group.