Database: customers_and_addresses
Question: Return the channel code and contact number of the customer contact channel whose active duration was the longest.
SQL:
SELECT channel_code ,  contact_number FROM customer_contact_channels WHERE active_to_date - active_from_date  =  (SELECT active_to_date - active_from_date FROM customer_contact_channels ORDER BY (active_to_date - active_from_date) DESC LIMIT 1)