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)
Return the channel code and contact number of the customer contact channel whose active duration was the longest.
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 )
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 value )
Return the channel code and contact number of the customer contact channel whose active duration was the longest .