+------------------+---------+
| Column Name      | Type    | 
+------------------+---------+
| event_id         | int     |
| user_id          | int     |
| event_date       | date    |
| event_type       | varchar |
| plan_name        | varchar |
| monthly_amount   | decimal |
+------------------+---------+
event_id is the unique identifier for this table.
event_type can be start, upgrade, downgrade, or cancel.
plan_name can be basic, standard, premium, or NULL (when event_type is cancel).
monthly_amount represents the monthly subscription cost after this event.
For cancel events, monthly_amount is 0.

Input:

subscription_events table:

+----------+---------+------------+------------+-----------+----------------+
| event_id | user_id | event_date | event_type | plan_name | monthly_amount |
+----------+---------+------------+------------+-----------+----------------+
| 1        | 501     | 2024-01-01 | start      | premium   | 29.99          |
| 2        | 501     | 2024-02-15 | downgrade  | standard  | 19.99          |
| 3        | 501     | 2024-03-20 | downgrade  | basic     | 9.99           |
| 4        | 502     | 2024-01-05 | start      | standard  | 19.99          |
| 5        | 502     | 2024-02-10 | upgrade    | premium   | 29.99          |
| 6        | 502     | 2024-03-15 | downgrade  | basic     | 9.99           |
| 7        | 503     | 2024-01-10 | start      | basic     | 9.99           |
| 8        | 503     | 2024-02-20 | upgrade    | standard  | 19.99          |
| 9        | 503     | 2024-03-25 | upgrade    | premium   | 29.99          |
| 10       | 504     | 2024-01-15 | start      | premium   | 29.99          |
| 11       | 504     | 2024-03-01 | downgrade  | standard  | 19.99          |
| 12       | 504     | 2024-03-30 | cancel     | NULL      | 0.00           |
| 13       | 505     | 2024-02-01 | start      | basic     | 9.99           |
| 14       | 505     | 2024-02-28 | upgrade    | standard  | 19.99          |
| 15       | 506     | 2024-01-20 | start      | premium   | 29.99          |
| 16       | 506     | 2024-03-10 | downgrade  | basic     | 9.99           |
+----------+---------+------------+------------+-----------+----------------+

Output:

+----------+--------------+------------------------+-----------------------+--------------------+
| user_id  | current_plan | current_monthly_amount | max_historical_amount | days_as_subscriber |
+----------+--------------+------------------------+-----------------------+--------------------+
| 501      | basic        | 9.99                   | 29.99                 | 79                 |
| 502      | basic        | 9.99                   | 29.99                 | 69                 |
+----------+--------------+------------------------+-----------------------+--------------------+

Explanation:

• User 501:
  • Currently active: Last event is downgrade to basic (not cancelled) 
  • Has downgrades: Yes, 2 downgrades in history 
  • Current revenue (9.99) vs max (29.99): 9.99/29.99 = 33.3% (less than 50%) 
  • Days as subscriber: Jan 1 to Mar 20 = 79 days (at least 60) 
  • Result: Churn Risk Customer
• User 502:
  • Currently active: Last event is downgrade to basic (not cancelled) 
  • Has downgrades: Yes, 1 downgrade in history 
  • Current revenue (9.99) vs max (29.99): 9.99/29.99 = 33.3% (less than 50%) 
  • Days as subscriber: Jan 5 to Mar 15 = 70 days (at least 60) 
  • Result: Churn Risk Customer
• User 503:
  • Currently active: Last event is upgrade to premium (not cancelled) 
  • Has downgrades: No downgrades in history 
  • Result: Not at-risk (no downgrade history)
• User 504:
  • Currently active: Last event is cancel
  • Result: Not at-risk (subscription cancelled)
• User 505:
  • Currently active: Last event is 'upgrade' to standard (not cancelled) 
  • Has downgrades: No downgrades in history 
  • Result: Not at-risk (no downgrade history)
• User 506:
  • Currently active: Last event is downgrade to basic (not cancelled) 
  • Has downgrades: Yes, 1 downgrade in history 
  • Current revenue (9.99) vs max (29.99): 9.99/29.99 = 33.3% (less than 50%) 
  • Days as subscriber: Jan 20 to Mar 10 = 50 days (less than 60) 
  • Result: Not at-risk (insufficient subscription duration)

Result table is ordered by days_as_subscriber DESC, then user_id ASC.

Note: days_as_subscriber is calculated from the first event date to the last event date for each user.