Are the customers holding coupons with amount 500 bad or good?
create table discount_coupons (coupon_id varchar, coupon_amount varchar, PRIMARY KEY (coupon_id)); create table customers (good_or_bad_customer varchar, coupon_id varchar, PRIMARY KEY (good_or_bad_customer))
select t1.good_or_bad_customer from customers as t1 join discount_coupons as t2 on t1.coupon_id = t2.coupon_id where t2.coupon_amount = 500