Write a query in domain relational calculus. The following relational database s

Question

Write a query in domain relational calculus.

The following relational database schema AUCTION models the business data of an online auction system: - PERSON={pid, pname, phone, location} with key {pid}, - ITEM={iid, iname, description, sid} with key {iid}, and foreign key [sid] PERSON[pid] - BID={bid, iid, price} with key {bid,iid,price}, and foreign keys [bid] PERSON[pid] [iid] ITEM [iid] - SALE={iid, bid, price} with key {iid}, and foreign keys [iid] Item [iid] [bid] Person [pid] [iid, bid, price] BlD[iid, bid, price] A double-bidding occurs whenever two different bidders bid for the same item at the same price. For each of the queries, do the following: - Write the query in Domain Relational Calculus. a. List the names and phone numbers of the bidders who are not always affected by double-bidding. b. List the names of bidders who have bid on every item that has sold.

Explanation / Answer

PERSON={pid,pname,phone, location} ={a,b,c,d}

ITEM={iid,iname, description,sid} = {p,q,r,s}

BID={bid,iid,price} ={x,y,z}

SALE={iid,bid,price}

a. { < a,b > | c,d ( < a, b ,c,d> person <x,y,z) bid}

b. { <a> | c (person(a,b,c,d) p (item(p,q,r,s)) y (bid(x,y,z)) }

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