The Hanover Insurance Group needs a monthly view of posted policy premiums for financial reporting. Write a PostgreSQL query that aggregates premiums by calendar month and calculates a cumulative total across months.
premium_status is posted.premium_date.| Column | Type | Description |
|---|---|---|
| premium_idPK | INT | Primary key for the premium record |
| policy_number | VARCHAR(20) | Hanover policy identifier |
| premium_date | DATE | Date the premium was recorded |
| premium_amount | DECIMAL(12,2) | Premium amount, which may be NULL |
| premium_status | VARCHAR(20) | Processing status of the premium record |