Below is an context that describes a sql query, paired with an question that provides further information. Write an answer that appropriately completes the request.  # noqa: E501
### Context:
CREATE TABLE customers (customer_id VARCHAR); CREATE TABLE orders (customer_id VARCHAR)
### Question:
What is the customer id of the customer who has the most orders?
### Answer:
SELECT T1.customer_id FROM customers AS T1 JOIN orders AS T2 ON T1.customer_id = T2.customer_id GROUP BY T1.customer_id ORDER BY COUNT(*) DESC LIMIT 1