CREATE TABLE customers (customer_id VARCHAR2, customer_name VARCHAR2)
CREATE TABLE customer_contact_channels (active_to_date NUMBER, customer_id VARCHAR2)

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