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

Question: What is the "active to date" of the latest contact channel used by "Tillman Ernser"?
SQL: SELECT MAX(t2.active_to_date) FROM customers AS t1 JOIN customer_contact_channels AS t2 ON t1.customer_id = t2.customer_id WHERE t1.customer_name = "Tillman Ernser"