Database Systems: The Complete Book
Solutions for Chapter 2
Solutions for Section 2.1
Exercise 2.1.1
The E/R Diagram.
Exercise 2.1.8(a)
The E/R Diagram
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Solutions for Section 2.2
Exercise 2.2.1
The Addresses entity set is nothing but a single address, so we would prefer to make address an
attribute of Customers. Were the bank to record several addresses for a customer,
then it might
make sense to have an Addresses entity set and make Lives-at a many-many relationship.
The Acct-Sets entity set is useless. Each customer has a unique account set containing his or her
accounts.
However,
relating
customers
directly
to
their
accounts
in
a
many-many
relationship
conveys the same information and eliminates the account-set concept altogether.
Solutions for Section 2.3
Exercise 2.3.1(a)
Keys ssNo and number are appropriate for Customers and Accounts, respectively. Also, we think
it does not make sense for an account to be related to zero customers, so we should round the edge
connecting Owns to Customers. It does not seem inappropriate to have a customer with 0 accounts;