WHERE value IS NOT IN (subquery)
问题 I've been struggling with this query. I have two tables. One with coupons and Invoicenumbers. One with Invoicenumbers and customer names. I need to get the customers who have not used a given coupon. Here are the tables: Promotion table: Promotions Invoice | Coupon ---------------- 1 | couponA 2 | couponB 3 | couponB Orders Table: Orders Invoice | Customer ------------------ 1 | Jack 2 | Jack 3 | Jill So Jack has used coupons A and B. And Jill has only used coupon B. If my query were select