RECALL

Question 1

What is a file-based system?

Answer 1

Is a collection of application programs that perform services for end-users. Each program defines and manages its own data.

Question 2

What are limitations of file-based systems?

Answer 2

Duplication of data.
Data independence.
Incompatible formats.
Separation and isolation of data.

Question 3

What is a database?

Answer 3

A shared collection of data and a description of the data, designed to meet to information needs of an organisation.

Question 4

What does a system catalog provide?

Answer 4

Provides a description of the data to enable program data independence.

Question 5

What is a Database Management System (DBMS)?

Answer 5

A system that enables users to create, manipulate, maintain a database.

Question 6

What is Data Definition Language? (DDL)

Answer 6

Allows database administrators and users to define and name entities, attributes and relationships.

Question 7

What is Data Manipulation Language? (DML)

Answer 7

Allows basic manipulation operations on the data in the database.

Question 8

There a three major components of the DBMS environment. What are these three?

Answer 8

Machine, bridge, human.

Question 9

Relating to machine, bridge and human, what does each of these involve?

Answer 9

Hardware = A pc or a network of pc’s.
Software = DBMS, operating system, network software, application program.
Data
Procedures = A set of instructions and rules that should be applied to the database and DBMS.
People

Question 10

What is the purpose of views?

Answer 10

Allows each user to have their own view of the database.

Question 11

What are some purposes of views?

Answer 11

Provide powerful and flexible security.
Allow users to have a customizable view of the database.
Can simply complex operations.

Question 12

What are some advantages of DBMS?

Answer 12

Sharing of data.
Improved concurrency.
Improved security.
Backup and recovery services.
Increased productivity.

Question 13

What are some disadvantages of DBMS?

Answer 13

Complexity.
Size.
Cost.
Higher impact of failure.

Question 14

What are the objectives of three-level architecture?

Answer 14

All users should be able to access the same data.
Users view should be immune to changes in other views.
Database administrator should be able to make changes in the storage structure and conceptual schema without affecting the users view.

Question 15

What are the three levels of three-level architecture? Describe them

Answer 15

External view = Users view of the database and describes the part of the database relevant to the user.
Conceptual view = Communities view of the database and defines data’s and what data is being stored
Internal view = Physical representation of the database.

Question 16

What is procedural DML?

Answer 16

Allows users to tell the system exactly how to manipulate data.

Question 17

What is non-procedural DML?

Answer 17

Allows users to state what data is needed.

Question 18

What is a data model and what is its purpose?

Answer 18

Is a collection of concepts describing the data, relationships between data and the constraints on the data. Its purpose is to represent the data in an understandable way.

Question 19

What is a relational model?

Answer 19

A table with column and rows.

Question 20

What does ‘attribute’ mean?

Answer 20

Named column.

Question 21

What is a domain?

Answer 21

A set of allowable values for one or more attributes.

Question 22

What is a tuple?

Answer 22

A row.

Question 23

What does degree mean?

Answer 23

The number of attributes in a relation.

Question 24

What does cardinality mean?

Answer 24

The number of tuples in a relation.

Question 25

What are some properties of relations?

Answer 25

Relation name is distinct from other relation names
Each cell of relation contains only one single value
Each attribute has a distinct name
No duplicate tuples
Values of an attribute are all from the same domain
Attribute and tuple order have no real significance

Question 26

There are 5 types of keys. Name them.

Answer 26

Super key, primary key, alternate key, candidate key, foreign key.

Question 27

What does the term multiplicity mean?

Answer 27

Number of possible occurrences of an entity type that may relate to a single occurrence of an associated entity type.

Question 28

What are the two types of traps in ER models.

Answer 28

Fan trap, chasm trap

Question 29

What is normalization?

Answer 29

A technique for producing a set of suitable relations that support the database requirements.

Question 30

What are some benefits of normalization?

Answer 30

Easier for the user to access and maintain data.

Take up minimal storage space on the computer.

Question 31

What are some characteristics of a suitable set of relations?

Answer 31

Minimal number of attributes necessary to support the data.
Attributes with a close logical relationship are found in the same relation.
Reduces redundancies in design.

Question 32

What is the point of normalization?

Answer 32

To determine if you gave redundancies in your design. Therefore a normalize design of your database will have less redundancies.

Question 33

What is unnormalized form?

Answer 33

A table the contains one or more repeating groups.

Question 34

What is First Normalized Form (1NF)?

Answer 34

A relation in which the intersection of each row and column contains one and only one value.

Question 35

What is Second Normal Form? (2NF)?

Answer 35

A relation that is 1NF and every non-primary-key attribute is fully functional dependent on the primary key.

Question 36

What is Third Normal Form (3NF)?

Answer 36

A relation that is 1NF and 2NF and which no non-primary-key is transitively independent on the primary key.