Database

Question 1

What is a data model?

Answer 1

An abstract model of which things to store and what information about them should be recorded

Question 2

Define an entity in the context of a database

Answer 2

A thing about which data is to be stored

Question 3

What are attributes in a database?

Answer 3

Characteristics or other information about entities

Question 4

How are databases structured?

Answer 4

Databases are formed of tables which are used to store multiple entities

Question 5

What does each row in a database table typically represent?

Answer 5

Each entity

Question 6

What is an entity identifier?

Answer 6

An attribute given to each entity which is unique within that table

Question 7

How can multiple attributes form an entity identifier?

Answer 7

Some database tables have multiple attributes which are combined to form the table’s entity identifier

Question 8

What is the purpose of an entity description?

Answer 8

To describe how information is to be stored about entities

Question 9

What is a primary key?

Answer 9

An attribute that provides a unique identifier for every entity in a database table

Question 10

What is a foreign key?

Answer 10

An attribute in a table which is the primary key in another, related table

Question 11

What is a link table?

Answer 11

A new table created when linking many-to-many relationships

Question 12

What is database normalization?

Answer 12

The process of organizing a database to minimize redundancy and improve data integrity

Question 13

What is the main goal of normalizing databases?

Answer 13

To ensure that entities contain no redundant or repeated data

Question 14

What are the advantages of a normalized database?

Answer 14

Faster searching and sorting, easier maintenance, minimized duplication, improved data consistency

Question 15

What characterizes a database in first normal form?

Answer 15

Must not contain any repeating attributes and has atomic data

Question 16

Define second normal form in databases

Answer 16

Must satisfy first normal form and have any partial key dependencies removed

Question 17

What is a partial key dependency?

Answer 17

Occurs when a non-key attribute doesn’t depend on the whole of the composite key

Question 18

What conditions must a database meet to be in third normal form?

Answer 18

Must conform to second normal form and have no non-key dependencies

Question 19

What does it mean when non-key attributes depend on the key?

Answer 19

All non-key attributes depend on the key, the whole key, and nothing but the key

Question 20

What are the three possible degrees of relationship between tables in a database?

Answer 20

• one-to-one
• one-to-many
• many-to-many

Question 21

Describe a one-to-one relationship with an example

Answer 21

Each car has one owner, and each owner has one car

Question 22

Describe a one-to-many relationship with an example

Answer 22

Each driver can drive many different cars. Each car is driven by many different drivers

Question 23

Describe a one to-many relationship with an example

Answer 23

Each car has many passengers. Each passenger sits in one car

Question 24

What does an entity relationship diagram represent?

Answer 24

Graphically represents the relationships between tables in a database