Task: Text to Code
Input (English): Step 1: For each row in Customers table, find the corresponding rows in Customer_Contact_Channels table.
Step 2: find the active_from_date in the results of step 1 whose customer_name equals Tillman Ernser with largest value of date_became_customer
Output (English): SELECT T2.active_from_date FROM Customers AS T1 JOIN Customer_Contact_Channels AS T2 ON T1.customer_id = T2.customer_id WHERE T1.customer_name = "Tillman Ernser" ORDER BY T1.date_became_customer Desc LIMIT 1