CREATE TABLE Discount_Coupons (coupon_amount VARCHAR(255), coupon_id VARCHAR(255)); CREATE TABLE customers (coupon_id VARCHAR(255), good_or_bad_customer VARCHAR(255))
What are the coupon amount of the coupons owned by both good and bad customers?
    
SQL: SELECT T1.coupon_amount FROM Discount_Coupons AS T1 JOIN customers AS T2 ON T1.coupon_id = T2.coupon_id WHERE T2.good_or_bad_customer = 'good' INTERSECT SELECT T1.coupon_amount FROM Discount_Coupons AS T1 JOIN customers AS T2 ON T1.coupon_id = T2.coupon_id WHERE T2.good_or_bad_customer = 'bad'