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)