How many more "discount" gas stations does the Czech Republic have compared to Slovakia?
Computation of more discount = Total no. of discount gas stations in Czech Republic - Total no. of discount gas stations in Slovakia
SELECT SUM(IIF(Country = 'CZE', 1, 0)) - SUM(IIF(Country = 'SVK', 1, 0)) FROM gasstations WHERE Segment = 'Discount'