CREATE TABLE customers (phone_number VARCHAR(255), customer_id VARCHAR(255)); CREATE TABLE complaints (customer_id VARCHAR(255), date_complaint_raised VARCHAR(255))
What is the phone number of the customer who has filed the most recent complaint?
    
SQL: SELECT t1.phone_number FROM customers AS t1 JOIN complaints AS t2 ON t1.customer_id = t2.customer_id ORDER BY t2.date_complaint_raised DESC LIMIT 1