【2017年整理】Solutions to Exercises(DBMS).docVIP

《Introduction to Database System》 Solutions to Exercises Li Ping Chapter 2 The Entity-Relationship Data Model Exercise 2.1.1: Let us design a database for a bank, including information about customers and their accounts. Information about a customer includes their name, address, phone, and Social Security number. Accounts have numbers, types (e.g., savings, checking) and balances. We also need to record the customer(s) who own an account. Draw the E/R diagram for this database. Be sure to include arrows where appropriate, to indicate the multiplicity of a relationship. P.36 Solution: Exercise 2.1.6: Suppose we wish to keep a genealogy. We shall have one entity set, People. The information we wish to record about persons includes their name(an attribute) and the following relationships: mother, father, and children. Given an E/R diagram involving the People entity set and all the relationships in which it is involved. Include relationships for mother, father, and children. Do not forget to indicate roles when an entity set is used more than once in a relationship. Solution: Exercise 2.2.1: In Fig. 2.14 is an E/R diagram for a bank database involving customers and accounts. Since customers may have several accounts, and accounts may be held joint by several customers, we associate with each customer an “account set”, and accounts are members of one or more account sets. Assuming the meaning of the various relationships and attributes are as expected given their names, criticize the design. What design rules are violated? Why? What modifications would you suggest? P.44 Solution: 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. 2. The Acct-Sets entity set is useless. Each customer has a unique account set conta