1193. Monthly Transactions I

SELECT
  DATE_FORMAT(trans_date, '%Y-%m') AS month,
  country,
  COUNT(*) AS trans_count,
  SUM(state = 'approved') AS approved_count,
  SUM(amount) AS trans_total_amount,
  SUM(IF(state = 'approved', amount, 0)) AS approved_total_amount
FROM Transactions
GROUP BY 1, 2;