Write a SQL query to retrieve the total number of shipments per month from a logistics database for DP world.
Use the shipments table and include only records with a non-null shipment date.
shipment_month and total_shipments.| Column | Type | Description |
|---|---|---|
| shipment_idPK | INT | Unique identifier for the shipment |
| shipment_date | DATE | Date on which the shipment was recorded |