Database Design and Relational Theory

Appendix D. Answers to Exercises

Science offers the best answers

—Richard Dawkins: Break the Science Barrier

Note: All mistakes in this appendix are deliberate <joke>.

CHAPTER 1

1.1 Yes, it is. Good design benefits the user, and to some extent the DBMS as well, but the relational model as such doesn’t care how the database happens to be designed, just so long as it doesn’t violate any of the precepts of the relational model—in particular, so long as the objects it has to deal with are indeed relations and not something else (which, sadly, they often are in SQL).

1.2 See Chapter 15.

1.3 See Chapter 4 and Chapter 5.

1.4 Yes (see Chapter 4 and Chapter 5).

1.5 No. (Actually, it’s not even true that every binary relvar is in 2NF. See Exercise 4.6.)

1.6 No (see Chapter 9 and Chapter 10).

1.7 No a fortiori, given the answer to Exercise 1.5.

1.8 No (see Chapter 13).

1.9 No (see Chapter 13).

1.10 See Chapter 10.

1.11 No (see Chapter 9 and Chapter 15).

1.12 See Chapter 8.

1.13 See Chapter 5.

1.14 See Chapter 14.

1.15 See Chapter 11.

1.16 See Chapter 7.

1.17 See Chapter 11.

1.18 See Chapter 13, also Appendix B.

CHAPTER 2

2.1 The Information Principle is a fundamental principle that underpins the entire relational model. It can be stated as follows:

• Definition: The Information Principle states that the only kind of variable allowed in a relational database is the relation variable or relvar. Equivalently, the entire information content of the database at any given time is represented in one and only one way—namely, ...