CREATE TABLE customers (customer_id VARCHAR2, customer_name VARCHAR2)
CREATE TABLE available_policies (policy_type_code VARCHAR2, policy_id VARCHAR2)
CREATE TABLE customers_policies (customer_id VARCHAR2, policy_id VARCHAR2)

What are all the policy types of the customer that has the most policies listed?
SELECT DISTINCT t3.policy_type_code FROM customers AS t1 JOIN customers_policies AS t2 ON t1.customer_id = t2.customer_id JOIN available_policies AS t3 ON t2.policy_id = t3.policy_id WHERE t1.customer_name = (SELECT t1.customer_name FROM customers AS t1 JOIN customers_policies AS t2 ON t1.customer_id = t2.customer_id GROUP BY t1.customer_name ORDER BY COUNT(*) DESC LIMIT 1)
WITH "_u_0" AS (SELECT "t1"."customer_name" FROM "customers" "t1" JOIN "customers_policies" "t2" ON "t1"."customer_id" = "t2"."customer_id" GROUP BY "t1"."customer_name" ORDER BY COUNT(*) DESC FETCH FIRST 1 ROWS ONLY) SELECT DISTINCT "t3"."policy_type_code" FROM "customers" "t1" JOIN "_u_0" "_u_0" ON "_u_0"."customer_name" = "t1"."customer_name" JOIN "customers_policies" "t2" ON "t1"."customer_id" = "t2"."customer_id" JOIN "available_policies" "t3" ON "t2"."policy_id" = "t3"."policy_id"