Homework 2
CS422,
Summer 2005
Due: Saturday, July 16
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[Reading]
- Textbook Chapter 3.6, 3.7 and 5.
[Exercises]
1. (10pt) Figure 2.15 in the textbook shows a 4-way relationship about Births. Assume that a mother can
give birth to more than one baby, and there could be more than one
doctor and/or nurse present at the birth, discuss why the 4-way
relationship is a bad design. [HINT: use your knowledge about how ER
relationships are translated into relations, and how we determine
whether a relation schema is good or not.]
2. (20pt) Exercise 3.6.1 (c) (e)
3. (20pt) Exercise 3.7.3 (b) (d)
4. (20pt) For a relation R(A, B, C, D), prove or give a counter-example
of the following:
(a) If AB ->-> BC, then AB
->-> B and AB ->-> C
(b) If A ->-> BC, then A ->-> B and A ->-> C
5. (20pt) Exercise 5.2.4 (e) (f) (g) (h)
6. (10pt) Exercise 5.5.1 (c) (e)