If you want to save a query as a CSV/xls etc., then it’s useful to separate the number and the currency into individual columns. Here is an example of monthly expenses and income for 2016 which does that.
SELECT
month, account, sum(number) as Total, currency
FROM
year = 2016
WHERE
account ~ 'Expenses' OR
account ~ 'Income'
GROUP BY month, account, currency
ORDER BY month, currency, account