Entity Relationship Diagrams

What is the purpose of an Entity Relationship Diagram (ERD)?

• To visualize the logical structure of databases
• To create flowcharts for data processes
• To store information about entities
• To represent relationships between entities

Which symbol is used to represent an entity in an ERD?

• Rectangle
• Diamond
• Oval
• Solid line

What does a weak entity represent in an ERD?

• An entity that must be defined by a foreign key relationship
• An entity that can be uniquely identified by its own attributes alone
• An entity that shares information with another entity
• An entity that has multiple relationships

What do diamond shapes represent in an ERD?

• Actions
• Attributes
• Entities
• Relationships

What is a key attribute in an ERD?

• A unique distinguishing characteristic of an entity
• An attribute with multiple values
• An attribute based on another attribute
• An attribute that represents an action

What does cardinality specify in an ERD?

• How many instances of an entity relate to one instance of another entity
• The absolute minimum number of relationships
• The maximum number of relationships
• The occurrences of a relationship

What does ordinality describe in an ERD?

• The relationship between entities
• The mandatory or optional nature of a relationship
• The maximum number of relationships
• The minimum number of relationships

Which notation style expresses cardinality in an ERD?

• Information engineering style
• Chen-style
• Bachmann style
• Martin style

How are ERD diagrams commonly used?

• In conjunction with data flow diagrams to display the contents of a data store
• To visualize the physical structure of databases
• To create algorithms for data processing
• To represent the flow of data in a system

What is the first step in making an ERD?

• Identifying all the entities
• Drawing rectangles for entities
• Describing relationships between entities
• Adding key attributes to entities