Database: debit_card_specializing
Question: What was the difference in gas consumption between CZK-paying customers and EUR-paying customers in 2012?
SQL: SELECT SUM(IIF(T1.Currency = 'CZK', T2.Consumption, 0)) - SUM(IIF(T1.Currency = 'EUR', T2.Consumption, 0)) FROM customers AS T1 INNER JOIN yearmonth AS T2 ON T1.CustomerID = T2.CustomerID WHERE SUBSTR(T2.Date, 1, 4) = '2012'