Lesson 2.4: Basics of the Relational Model

Question 1

The relational model gives us a single way to represent data: as a two-dimensional table called a

Answer 1

relation.

Question 2

The columns of a relation are named by

Answer 2

Attributes

Question 3

attributes appear at the

Answer 3

top of the columns

Question 4

The name of a relation and the set of attributes for a relation is called the ____ for that relation.

Answer 4

schema

Question 5

The attributes in a relation schema are a ___, not a list.

Answer 5

set

Question 6

In the relational model, a database consists of one or more relations. The set of schemas for the relations of a database is called a _____ or just a __________-

Answer 6

relational database schema, or just a database schema.

Question 7

the rows of a relation, other than the header row containing the attribute names

Answer 7

tuples

Question 8

We shall generally follow the convention that relation names begin with a _______, and attribute names begin with a ______.

Answer 8

capital letter

lower-case letter

Question 9

t/f Relations are set of tuples, not lists of tuples

Answer 9

true

Question 10

t/f it is not possible to reorder the attributes of the relation

Answer 10

false.

Moreover, we can reorder the attributes of the relation as we choose, without changing the relation.

However, when we reorder the relation schema, we must be careful to remember that the attributes are column headers.

Question 11

t/f relations change over time

Answer 11

true

Question 12

A set of attributes forms a key for a relation if we do not allow two tuples in a relation instance to have the same values in all the attributes of the key.

Answer 12

key constraints