Table schema:
CREATE TABLE customers (customer_id VARCHAR, customer_name VARCHAR); CREATE TABLE customer_contact_channels (customer_id VARCHAR)

Question: Which contact channel has been used by the customer with name "Tillman Ernser"?
SQL: SELECT DISTINCT channel_code FROM customers AS t1 JOIN customer_contact_channels AS t2 ON t1.customer_id = t2.customer_id WHERE t1.customer_name = "Tillman Ernser"