CREATE TABLE policies (start_date INT)
CREATE TABLE customers (customer_details VARCHAR, customer_id VARCHAR)

Which customer is associated with the latest policy?
SELECT t2.customer_details FROM policies AS t1 JOIN customers AS t2 ON t1.customer_id = t2.customer_id WHERE t1.start_date = (SELECT MAX(start_date) FROM policies)
SELECT "t2"."customer_details" FROM "policies" AS "t1" JOIN "customers" AS "t2" ON "t1"."customer_id" = "t2"."customer_id" WHERE "t1"."start_date" = (SELECT MAX("start_date") FROM "policies")