In SQL

Find all undervalued sales that have the term xbox in their descriptions; a sale s is undervalued if it is associated to a product p and p is associated with another sale s' and the highest bid for s' is more than twice the amount of the highest bid for s. Matching of the keyword xbox must be case-insensitive. For each qualifying sale s, list sid, lister of the sale, pid of the product associated with the sale and the maximum bid amount offered for the sale.

users(email, name, pwd, city, gender) products(pid, descr) sales(sid, lister, pid, edate, descr, cond, rprice) bids(bid, bidder, sid, bdate, amount) items(sid, no, pid, descr) reviews(reviewer, reviewee, rating, rtext, rdate) previews(rid, pid, reviewer, rating, rtext, rdate)