What are the coupon amount of the coupons owned by both good and bad customers?
CREATE TABLE Discount_Coupons (coupon_amount VARCHAR, coupon_id VARCHAR); CREATE TABLE customers (coupon_id VARCHAR, good_or_bad_customer VARCHAR)
[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' [/SQL]