Write a SQL query to join customer and order tables and return the total order amount per customer.
Return every customer, including customers without orders. Treat customers with no non-null order amounts as having a total of zero.
customer_id, customer_name, and total_order_amount.customer_id in ascending order.| Column | Type | Description |
|---|---|---|
| customer_idPK | INT | Unique customer identifier |
| customer_name | VARCHAR(100) | Customer's full name |
| Column | Type | Description |
|---|---|---|
| order_idPK | INT | Unique order identifier |
| customer_id | INT | Identifier of the customer who placed the order |
| order_amount | NUMERIC(10,2) | monetary amount for the order |