Consider an online auction database system in which members (buyers and sellers) participate in the sale of items. The data requirements for this system are summarized as follows: Members The online site has members who are identified by a unique member id and are described by an email address, their name, a password, their home address, and a phone number. Supertype and Subtypes for Members A member may be a buyer or a seller, but not both (disjoint subtype). A member must be one or the other (mandatory or required participation). A buyer has a shipping address recorded in the database. A seller has a bank account number and routing number recorded in the database. Both buyer and seller subtypes (entities) share the primary key with members which is membered. Items Items are placed by a seller for sale and are identified by a unique item number assigned by the system. Items are also described by an item title, an item description, a starting bid price, bidding increment, the start date of the auction, and the end date of the auction. Items also have a classification attribute which classifies the item as a type. Many to many relationship Buyers place one to many bids on items. Items have one to many bids from buyers. This is a many to many relationship and you need to add a “linking” or “Associative” third table between Items and Buyers with a TransactionID (primary key) membered (from the buyertable) – foreign key, ItemID – foreign key, and a bidding price and date/time stamp of the bid. Draw an enhanced entity-relationship diagram
Consider an online auction
participate in the sale of items. The data requirements for this system are summarized as
follows:
Members
The online site has members who are identified by a unique member id and are
described by an email address, their name, a password, their home address, and a
phone number.
Supertype and Subtypes for Members
A member may be a buyer or a seller, but not both (disjoint subtype). A member must be one or the other (mandatory or required participation). A buyer has a shipping address recorded in the
database. A seller has a bank account number and routing number recorded in the
database. Both buyer and seller subtypes (entities) share the primary key with members which is membered.
Items
Items are placed by a seller for sale and are identified by a unique item number
assigned by the system. Items are also described by an item title, an item description,
a starting bid price, bidding increment, the start date of the auction, and the end date
of the auction. Items also have a classification attribute which classifies the item as a type.
Many to many relationship
Buyers place one to many bids on items. Items have one to many bids from buyers. This is a many to many relationship and you need to add a “linking” or “Associative” third table between Items and Buyers with a TransactionID (primary key) membered (from the buyertable) – foreign key, ItemID – foreign key, and a bidding price and date/time stamp of the bid.
Draw an enhanced entity-relationship diagram
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