IS 350 05.02 Transforming ER Diagrams to Relational Models

What is an entity set?

• A collection of entities that share common property values
• A collection of relations that share common keys
• A collection of attributes that describe an entity
• A collection of entities of the same type

What is an attribute?

• A property or characteristic of an entity
• A value or data item associated with an entity
• A value or data item associated with a key
• A relationship or association between entities

What is a relation?

• A table with rows and columns
• A graph with nodes and edges
• A function with inputs and outputs
• A set with elements and subsets

What is an instance identifier attribute?

• An attribute that specifies the type of an entity
• An attribute that indicates the status of an entity
• An attribute that uniquely identifies an entity in an entity set
• An attribute that links an entity to another entity

What is a key for a relation?

• A column or combination of columns that has no null values
• A column or combination of columns that has unique values
• A column or combination of columns that uniquely identifies each row
• A column or combination of columns that references another relation

What is a specialization/generalization entity in an entity-relationship (ER) model?

• An entity that represents a many-to-many relationship between two other entities
• An entity that represents a relationship between two other entities
• An entity that represents a more specific version of a general entity
• An entity that cannot be transformed into a relation in a relational data model

What is a disjoint specialization in an ER model?

• A specialization in which each instance of the general entity belongs to one and only one subclass entity
• A specialization in which each instance of the general entity can belong to multiple subclass entities
• A specialization that cannot be transformed into a relation in a relational data model
• A type of relationship entity in an ER model

How can you represent a specialization in a relational data model?

• By creating a new table for each subclass entity
• By adding a field to the general entity that specifies the subclass entity
• By adding a field to each subclass entity that references the primary key of the general entity
• By creating a composite entity that contains the primary keys of the general entity and each subclass entity

What is an overlapping specialization in an ER model?

• A specialization in which each instance of the general entity belongs to one and only one subclass entity
• A specialization in which each instance of the general entity can belong to multiple subclass entities
• A specialization that cannot be transformed into a relation in a relational data model
• A type of relationship entity in an ER model

What is a one-to-one relationship in an entity-relationship model?

• A relationship where each entity of one entity set is related to exactly one entity of another entity set
• A relationship where each entity of one entity set is related to at most one entity of another entity set
• A relationship where each entity of one entity set is related to many entities of another entity set
• A relationship where many entities of one entity set are related to many entities of another entity set