1193. Monthly Transactions I.sql.sql

Create table If Not Exists Transactions (id int, country varchar(4), state enum('approved', 'declined'), amount int, trans_date date);
insert into Transactions (id, country, state, amount, trans_date) values ('121', 'US', 'approved', '1000', '2018-12-18');
insert into Transactions (id, country, state, amount, trans_date) values ('122', 'US', 'declined', '2000', '2018-12-19');
insert into Transactions (id, country, state, amount, trans_date) values ('123', 'US', 'approved', '2000', '2019-01-01');
insert into Transactions (id, country, state, amount, trans_date) values ('124', 'DE', 'approved', '2000', '2019-01-07');
SELECT * FROM Transactions;


/* Output: 
+----------+---------+-------------+----------------+--------------------+-----------------------+
| month    | country | trans_count | approved_count | trans_total_amount | approved_total_amount |
+----------+---------+-------------+----------------+--------------------+-----------------------+
| 2018-12  | US      | 2           | 1              | 3000               | 1000                  |
| 2019-01  | US      | 1           | 1              | 2000               | 2000                  |
| 2019-01  | DE      | 1           | 1              | 2000               | 2000                  |
+----------+---------+-------------+----------------+--------------------+-----------------------+ */

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