What are the type codes of the policies used by the customer "Dayana Robel"?
SELECT policy_type_code FROM policies AS t1 JOIN customers AS t2 ON t1.customer_id  =  t2.customer_id WHERE t2.customer_details  =  "Dayana Robel"
type codes of the policies used by the customer 'Dayana Robel' refers to policy_type_code; joining tables policies and customers on customer_id; customer's name is stored in customer_details;