Terms

Question 1

What does ERM stand for?

Answer 1

Entity Relationship Model

Question 2

D: Entity Relationship Model

Answer 2

Conceptual database as viewed by end user that has the main components.

• Entities
• Atributes
• Relationships

Question 3

Entity

Answer 3

Refers to the entity set and not to a single entity occurrence

Question 4

D: Required Attributes

Answer 4

Attributes that must have a value, the value can not be left blank.

Question 5

D: Optional Attribute

Answer 5

Attributes that do not require a value, and can be left empty.

Question 6

D: Domain

Answer 6

Set of possible values for a given attribute.

Question 7

D: Identifiers

Answer 7

One or more attributes that uniquely identify each entity instance.

Question 8

D: Composite Identifier

Answer 8

Primary key composed of more then one attribute.

Question 9

D: Composite Attribute

Answer 9

Attribute that can be subdivided to yield additional attributes (if the attribute can be broken down more)

Question 10

D: Simple Attribute

Answer 10

Attribute that cannot be subdivided (attribute that can not be broke down any more)

Question 11

D: Single-Valued Attribute

Answer 11

Attribute that has only a single value

Question 12

D: Multivalued Attributes

Answer 12

Attributes that have many values and require creating several new attributes. One for each component of the original multivalued attribute.

Question 13

D: Derived Attribute

Answer 13

Attribute whose value is calculated from other attributes - derived using an algorithm. Ex - Obtaining your age from your date of birth.

Question 14

What is the problem with null values?

Answer 14

The problem is you don’t know if the value was left blank by mistake.

Question 15

What kind of data do you want to store in your database?Why?

Answer 15

• Final Data.

- Because this data doesn’t change (date of birth instead of how old you are)

Question 16

D: Relationships

Answer 16

Association between entities that always operate in both directions.

Question 17

D: Participants

Answer 17

Entities that are involved in a relationship.

Question 18

D: Connectivity

Answer 18

Describes the relationship classification. (The numbers of the relationship)

Question 19

D: Cardinality

Answer 19

Express the minimum and maximum number of entity occurrence associated with one occurrence of related entity. (The symbols of the relationship)

Question 20

D: Existence Dependence

Answer 20

Entity that exists on the database only when it is associated with another related occurrence.

Question 21

D: Existence Independence

Answer 21

• Entity exists apart from all of its related entities

- Referred to a strong entity or regular entity.

Question 22

D: Weak (non-identifying) relationship.

Answer 22

Primary key of the related entity does not contain a primary key component of the parent entity.

Question 23

How is a weak relationship represented in an ERD diagram?

Answer 23

With a dotted line

Question 24

D: Strong (identifying) relationships

Answer 24

Primary key of the related entry contains a primary key component of the parent entity.

Question 25

How is a strong relationship represented in anERD diagram?

Answer 25

With a solid line

Question 26

Does the strength of the relationship determine the strength of the entity?

Answer 26

No

Question 27

D: Optional Participation

Answer 27

One entity occurrence does not require a corresponding entity occurrence in a particular relationship

Question 28

D: Mandatory participation

Answer 28

One entity occurrence requires a corresponding entity occurrence in a particular relationship.