The Entity-Relationship Model

What does an entity in an ER model represent?

• A database

• A unique real-world object

• A collection of attributes

• A relationship

What is an entity set?

• A group of relationships

• A collection of similar entities

• A set of attributes

• A database schema

What is a super key?

• A set of attributes that uniquely identifies an entity

• A primary key in a weak entity

• A minimal attribute set for identification

• A foreign key reference

What does the ER model use to represent relationships?

• Rectangles

• Diamonds

• Circles

• Lines

Which of the following is not part of an ER diagram?

• Entities

• Attributes

• Indexes

• Relationships

What does a primary key represent in an ER diagram?

• A foreign key in another table

• The most important attribute

• A candidate key chosen for entity identification

• A relationship set identifier

What does the participation constraint describe?

• Entity uniqueness

• Relationship cardinality

• Mandatory or optional participation in a relationship

• Attribute dependencies

Which of these is a weak entity?

• An entity without a key attribute

• An entity with no attributes

• An entity with only foreign keys

• An entity dependent on another entity for identification

What symbol is used for total participation in ER diagrams?

• A solid line

• A dashed line

• A double line

• A single line

What is a binary relationship in an ER model?

• A relationship between two entities

• A relationship with two attributes

• A hierarchical relationship

• A cyclic relationship