CREATE TABLE customers (customer_id NUMBER, customer_details CLOB)
CREATE TABLE settlements (settlement_id NUMBER, claim_id NUMBER, date_claim_made TIME, date_claim_settled TIME, amount_claimed NUMBER, amount_settled NUMBER, customer_policy_id NUMBER)
CREATE TABLE claims (claim_id NUMBER, policy_id NUMBER, date_claim_made TIME, date_claim_settled TIME, amount_claimed NUMBER, amount_settled NUMBER)
CREATE TABLE payments (payment_id NUMBER, settlement_id NUMBER, payment_method_code CLOB, date_payment_made TIME, amount_payment NUMBER)
CREATE TABLE customer_policies (policy_id NUMBER, customer_id NUMBER, policy_type_code CLOB, start_date TIME, end_date TIME)

Find the policy type the most customers choose.
SELECT policy_type_code FROM customer_policies GROUP BY policy_type_code ORDER BY COUNT(*) DESC LIMIT 1
SELECT "policy_type_code" FROM "customer_policies" GROUP BY "policy_type_code" ORDER BY COUNT(*) DESC FETCH FIRST 1 ROWS ONLY