Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE orders ( customer_id VARCHAR )
TABLE: CREATE TABLE customers ( customer_id VARCHAR )

### Question ###
What is the customer id of the customer who has the most orders?

### Accurate SQL ###

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