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数据库CH (2)

数据库CH (2)

Introduction to the Relational Model

This chapter presents the relational model and a brief introduction to the relational-

algebra query language.The short introduction to relational algebra is sufficient

for courses that focus on application development,without going into database

internals.In particular,the chapters on SQL do not require any further knowl-

edge of relational algebra.However,courses that cover internals,in particular

query processing,require a more detailed coverage of relational algebra,which

is provided in Chapter6.

Exercises

2.9Consider the bank database of Figure2.15.

a.What are the appropriate primary keys?

employee(person name,street,city)

works(person name,company name,salary)

company(company name,city)

Figure2.14Relational database for Exercises2.1,2.7,and2.12.

branch(branch name,branch city,assets)

customer(customer name,customer street,customer city)

loan(loan number,branch name,amount)

borrower(customer name,loan number)

account(account number,branch name,balance)

depositor(customer name,account number)

Figure2.15Banking database for Exercises2.8,2.9,and2.13.

7

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