You are given Acumen transaction data and a product mapping table. Write a PostgreSQL query that breaks down performance by business line, returning each business line’s total revenue, transaction count, and average revenue per transaction. Any transaction whose product has a null or missing business line should be grouped into an Unmapped bucket.
| Column | Type | Description |
|---|---|---|
| transaction_idPK | INT | Unique transaction identifier |
| product_id | INT | Product sold in the transaction |
| transaction_date | DATE | Transaction date |
| revenue | NUMERIC(12,2) | Revenue recognized on the transaction |
| Column | Type | Description |
|---|---|---|
| product_idPK | INT | Product identifier |
| product_name | VARCHAR(100) | Product name |
| business_line | VARCHAR(50) | Business line assigned to the product |