Monthly transactions i

#
# Table: Transactions
# +---------------+---------+
# | Column Name   | Type    |
# +---------------+---------+
# | id            | int     |
# | country       | varchar |
# | state         | enum    |
# | amount        | int     |
# | trans_date    | date    |
# +---------------+---------+
# id is the primary key of this table.
# The table has information about incoming transactions.
# The state column is an enum of type ["approved", "declined"].
# Write an SQL query to find for each month and country, the number of transactions and their total amount, the number of approved transactions and their total amount.
# Return the result table in any order.
# The query result format is in the following example.
# Example 1:
# Input:
# Transactions table:
# +------+---------+----------+--------+------------+
# | id   | country | state    | amount | trans_date |
# +------+---------+----------+--------+------------+
# | 121  | US      | approved | 1000   | 2018-12-18 |
# | 122  | US      | declined | 2000   | 2018-12-19 |
# | 123  | US      | approved | 2000   | 2019-01-01 |
# | 124  | DE      | approved | 2000   | 2019-01-07 |
# +------+---------+----------+--------+------------+
# 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                  |
# +----------+---------+-------------+----------------+--------------------+-----------------------+
#

# Write your MySQL query statement below

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(CASE WHEN state = 'approved' THEN amount ELSE 0 END) AS approved_total_amount
FROM Transactions
GROUP BY DATE_FORMAT(trans_date, '%Y-%m'), country;