FedEx Business Intelligence analysts use regional shipment summaries to support network planning and operational reporting. Write a PostgreSQL query to identify the top five regions by total package volume.
package_count for each region, treating regions without shipments as volume 0.| Column | Type | Description |
|---|---|---|
| region_idPK | INTEGER | Unique identifier for a FedEx operating region |
| region_name | VARCHAR(50) | Name of the operating region |
| Column | Type | Description |
|---|---|---|
| shipment_idPK | INTEGER | Unique shipment record identifier |
| region_id | INTEGER | Referenced operating region; NULL indicates an unassigned shipment |
| package_count | INTEGER | Number of packages represented by the shipment record |