What is the customer id of Devin Mills.
SELECT DISTINCT t1.customer_id FROM customers AS t1 JOIN customer_contact_channels AS t2 ON t1.customer_id   =   t2.customer_id WHERE t1.customer_name  =  "Devin Mills"
customer id of a specific person refers to selecting customer_id from the customers table where customer_name matches; DISTINCT is used to ensure unique customer_id values; JOIN operation may be required to link multiple tables based on a common key.