Important Data Concept

chapter 4

The Relational Model and Normalization

True-False Questions

1. A relation is a three-dimensional table.

Answer: False Level: moderate

Page: 120

2. A characteristic of a relation is that the cells of the relation hold a single value.

Answer: True Level: easy

Page: 120

3. A characteristic of a relation is that the rows of a relation may hold identical values.

Answer: False Level: moderate

Page: 120

4. The columns of a relation are sometimes called “tuples.”

Answer: False Level: easy

Page: 122

5. Keys are always unique.

Answer: False Level: easy

Page: 122

6. A tuple is a group of one or more columns that uniquely identifies a row.

Answer: False Level: easy

Page: 122

7. A row can be uniquely identified by a key.

Answer: True Level: easy

Page: 122

8. A key can be composed of a group of attributes taken together.

Answer: True Level: easy

Page: 122

9. It is possible to have a relation that does not have a key.

Answer: False Level: hard

Page: 123

10. Attribute Y is functionally dependent on attribute X if the value of attribute X determines

the value of Y.

Answer: True Level: moderate

Page: 123

11. The functional dependency noted as A ( B, means that the value of A can be determined

from the value of B.

Answer: False Level: easy

Page: 123

12. In the functional dependency shown as A ( B, B is the determinant.

Answer: False Level: moderate

Page: 123

13. Functional dependencies can involve groups of attributes.

Answer: True Level: easy

Page: 124

14. A determinant of a functional dependency may or may not be unique in a relation.

Answer: True Level: moderate

Page: 125

15. A primary key...