Week 3

Question 1

What is a relation?

Answer 1

A table with columns and rows

Question 2

What is an attribute?

Answer 2

A named column of a relation (table)

Question 3

What is a domain?

Answer 3

A set of allowable values for one or more attributes.

Question 4

What is a tuple?

Answer 4

A row

Question 5

What does ‘degree’ mean?

Answer 5

The number of attributes in a relation (table)

Question 6

What does ‘cardinality’ mean?

Answer 6

Number of tuples in a relation (table)

Question 7

What are some properties of database relations?

Answer 7

Relation name is distinct from all other relation names
Each cell in a relation contain one and only one value
Each attribute has a distinct name
There are no duplicate tuples (rows)
Order of attributes have no significance

Question 8

What is a foreign key?

Answer 8

Is an attribute in one relation that is also a primary key in another relation

Question 9

What does entity integrity mean?

Answer 9

In a base relation, no attribute of a primary key can be null

Question 10

What does referential integrity mean?

Answer 10

If a foreign key exists in a relation, either the foreign key value must match the candidate key value of some tuple in its home relation OR foreign key value must be null

Question 11

What are some functions of a system catalog?

Answer 11

Provides powerful and flexible security
Allows users to access data in a customized way
Can simplify complex operations on base relations