Rolling 7-Day Shipments

Write a SQL query using window functions to calculate a rolling 7-day average of shipments by route for Leaf Logistics.

Use calendar days between each route's first and last shipment date, treating days without shipments as zero. Exclude records with a missing route or shipment date.

Output

1. One row per route and calendar day in that route's date range.
2. Columns: route_id, shipment_date, daily_shipments, and rolling_7_day_avg.
3. Round rolling_7_day_avg to two decimal places and order by route_id, then shipment_date.