Module 0 + 1

Question 1

What is data?

Answer 1

Facts and statistics gathers for analysis, usually digitized.

Question 2

What is information?

Answer 2

Data put into meaningful and useful context and given to the appropriate audience for them to use.

Question 3

What is a information?

Answer 3

System that manages information.

Question 4

What are the key building blocks of an information system?

Answer 4

• Inputs
• Processes
• Outputs
• Databases
• Technology

Question 5

What is a database?

Answer 5

An organized collection of related data.

Question 6

What is a DBMS?

Answer 6

Database management system.

Question 7

General functions of DBMS?

Answer 7

• Defining a database (specifying types, structures, and constraints for the data)
• Constructing a database (Storing the data on a medium)
• Manipulating a database (Querying and updating the database)
• Maintaining a database (Ensuring database efficiency, correctness and safety)

Question 8

What are the components of a database system?

Answer 8

• The stored database
• The DBMS
• The applications (to manipulate the data)
• The users (people who use the DBMS to interact with the database)

Question 9

What is conceptual database design?

Answer 9

Important phase in designing a database application.
Step 1: Universe of Discourse (UoD). Also known as the mini-world. It is the context in which the system will be.
Step 2: Converting UoD to a data model.

Question 10

What is normalization?

Answer 10

Removing redundancies (removing duplicate data)

Question 11

Why are redundancies bad?

Answer 11

• Extra work
• Waste of storage
• Inconsistent data

Question 12

What is a relational data model?

Answer 12

Visual representation of the relationship between collections of data.

Question 13

What is data integrity maintenance?

Answer 13

The DBMS must define and enforce constraints on the data based on semantics (rules defined according to context).

Question 14

What is query processing?

Answer 14

DBMS ability to run queries (questions about the data) and return data (answer said questions).

Question 15

Is the DBMS capable of security management?

Answer 15

Yes

Question 16

What are the three parts of Three-Schema Architecture?

Answer 16

• External level
• Conceptual level
• Internal level

Question 17

What is the external level responsible for (Three-Schema Architecture)

Answer 17

Provides access to particular parts of the database to users.

Question 18

What is the conceptual level responsible for (Three-Schema Architecture)

Answer 18

Describes the structure of the whole database for a community of users.

Question 19

What is the internal level responsible for (Three-Schema Architecture)

Answer 19

Describes the physical storage structures of the database.

Question 20

What is data independence via the Three-Schema Architecture?

Answer 20

Ability to change the schema at one level without having to change the schema at the next higher level.

Question 21

Logical data vs physical data independence?

Answer 21

Logical: change conceptual without changing the eternal views.
Physical: change the hardware without changing logical schema.

Question 22

What is a entity-relationship (ER) model/diagram?

Answer 22

Graphical data modelling technique that represents relationships between main entities.

Question 23

What is a entity?

Answer 23

Object with physical or conceptual existence. Each entity has attributes (attributes are particular properties).

Question 24

What is entity type?

Answer 24

What the combination of name and attributes describe.

Question 25

What is the most important key constraint?

Answer 25

Keys must be unique.

Question 26

Composite vs simple attributes? Differences?

Answer 26

Composite attributes can be divided into smaller parts which represent simple attributes with independent meaning. E.g. name (composite attribute) can be divided into first, middle, and last name.

Question 27

Several attribute keys

Answer 27

Entity keys composed of multiple attributes. Combination of attributes that make the key must be unique since keys still need to be unique no matter their composition.

Question 28

Single vs multi-value attributes. How are they represented in a ERD?

Answer 28

Multi-value attributes are double ovals while singles are one oval.

Question 29

Stored vs derived attributes

Answer 29

When an attribute is derived from a related attribute. E.g. age can be derived from birth date. Represented with a dotted-line oval.

Question 30

What are value sets of attributes?

Answer 30

Specified range for a particular attribute. E.g. age can only be between x and y.

Question 31

What is an entity set?

Answer 31

Collection of entities of a particular entity type. E.g. set of employees.

Question 32

What is a relationship?

Answer 32

Association among two or more entities. Symbol used is diamond.

Question 33

What are descriptive attributes?

Answer 33

Attributes for the relationship. Relationships may also have key attributes.

Question 34

What are the 3 relationship degrees? How many entities involved with each?

Answer 34

- Binary 2 - Ternary 3 - N-ary n

Question 35

What are entity roles?

Answer 35

Role (label) that a entity plays in a relationship instance. E.g. department and employee -> employer and worker.

Question 36

Recursive relationships?

Answer 36

Only one entity involved. E.g. employee in "manages" relationship. An employee can work for as well as manage another employee.

Question 37

Relationship set?

Answer 37

Collection of relationships of the same type. E.g. a bunch of different relationships representing what projects different employees are working on.

Question 38

Relationship contraints?

Answer 38

Limit the combination of entities that may participate. - cardinality constraints (ratio of entities) - participation constraints (total participation and partial participation)

Question 39

Existence dependency?

Answer 39

Existence of another entity depends on its relationship to another entity. E.g. every employee must work for a department. (Total participation and represented using a double line) E.g. not every employee is a manager. (Partial participation)

Question 40

Weak entities?

Answer 40

Do not have key attributes of their own. E.g. dependent of an employee. They have partial keys (attribute of the owner entity) that have dotted underlines. Weak entities always have total participation. Relationship related to a weak entity must also have double lines and is called the IDENTIFYING RELATIONSHIP.

Question 41

Enhanced entity relationship (ERR) model?

Answer 41

Entity type is called class. Subclasses and superclass. Attributes of superclass are inherited. Represented with the U symbol (open side is towards the subclass). Subclasses can have their own unique attributes.

Question 42

Specialization vs generalization?

Answer 42

Specialization: deriving subclasses from a superclass. Generalization: Abstracting similar entities into one superclass.

Question 43

EER constraints?

Answer 43

Total = double line Partial = single line Overlapping = circled o Disjoint = circled d