Porter Operations needs to monitor how long active drivers take to complete deliveries. Write a PostgreSQL query that calculates each active driver's average completed delivery time.
completed and both pickup and delivery timestamps present.NULL when a driver has no eligible deliveries.| Column | Type | Description |
|---|---|---|
| driver_idPK | INTEGER | Unique driver identifier |
| driver_name | VARCHAR(100) | Driver's name |
| driver_status | VARCHAR(20) | Current driver status |
| Column | Type | Description |
|---|---|---|
| delivery_idPK | INTEGER | Unique delivery identifier |
| driver_id | INTEGER | Assigned driver identifier |
| delivery_status | VARCHAR(20) | Current delivery status |
| picked_up_at | TIMESTAMPTZ | Pickup timestamp |
| delivered_at | TIMESTAMPTZ | Delivery completion timestamp |