Topic 4: Entity Relationship (ER) Modeling

Question 1

It forms the basis of an ERD

Answer 1

Entity Relationship Model

Question 2

It refers to attributes that must have a value at the time the instance is added. Null is not allowed

Answer 2

Required Attributes

Question 3

It is an attribute that allows to be left empty at the time the instance is added

Answer 3

Optional Attribute

Question 4

It refers to the set of possible values that an attribute can contain

Answer 4

Domains

Question 5

It refers to an attribute or set of attributes taht is used to differentitate one entity instance from another

Answer 5

Identifiers (Primary Keys)

Question 6

It refers to a primary key that is composed of more than one attribute

Answer 6

Composite Identifiers (Composite Keys)

Question 7

It is an attribute that can be subdivided into new several attributes

Answer 7

Composite Attributes

Question 8

It refers to an attribute that cannot be subdivided into several new attributes

Answer 8

Simple Attributes

Question 9

It is an attribute that can have a single value

Answer 9

Single-valued attributes

Question 10

it refers to attributes that can have many values

Answer 10

Multivalued Attributes

Question 11

How to implement multi-valued attributes?

Answer 11

• Creating several new attributes for the multi-valued attribute
• Create a new entity of the original multivalued attributes

Question 12

It is an attribute whose value is calculated from other attributes

Answer 12

Derived Attributes

Question 13

Advantages of Storing a Derived Attribute

Answer 13

• Saves CPU Processing Cycles
• Saves data access time
• Data value is readily available
• Can keep track of historic data

Question 14

Disadvantages of Storing Derived Attributes

Answer 14

• Requires constant maintance to ensure derived value is current

Question 15

Advantages of Not Storing Derived Attributes

Answer 15

• Saves storage space
• Computation always yields current value

Question 16

Disadvantages of Not Storing Derived Attributes

Answer 16

• Uses CPU processing cycles
• Increases data access time
• Adds coding complexity to queries

Question 17

It refers to the minimum and maximum number of entity occurrences associated with one occcurence of the related entity

Answer 17

Cardinality

Question 18

It is a relationship between entities wherrein the primary key of the related entity does not contain a PK component of the parent entity

Answer 18

Weak (non-identifying) Relationship

Question 19

It is a relationship between entities wherein the PK of the related entity contains a PK component of the parent entity

Answer 19

Strong (Identifying Relationships)

Question 20

It is an entity type whose existence depends on some other entity type

Answer 20

Weak Entity

Question 20

It is an entity type that exists independently of the other entity type

Answer 20

Strong Entity

Question 21

It is a type of relationship participation that one entity occurrence does not require a corresponding entity occurence in a particular relationship (min. is 0)

Answer 21

Optional Participation

Question 22

It is a type of participation wherein one entity occurence requires a corresponding entity occurence

Answer 22

Mandatory Participation

Question 23

It refers to the number of entities or participants associated with a relationship

Answer 23

Relationship Degree

Question 24

It is a realtionship degree when an association is maintained within a single entity

Answer 24

Unary Relationship

Question 25

It is another name for a unary relationship

Answer 25

Recursive Relationship

Question 26

It is a relationship degree wherein two entities are associated in a relationship; it is the most common relationship

Answer 26

Binary Relationship

Question 27

It is a relationship degree wherein there is an association among three different entities

Answer 27

Ternary Relationship

Question 28

When dealing with Ternary and Higher Relationships

Answer 28

It must be decomposed into appropriate equivalent binary relationships