ERDs Flashcards
What is an Entity Relationship Diagram (ERD)?
An Entity Relationship Diagram (ERD) is a visual representation of the relationships between entities in a database.
What is an entity in an ERD?
An entity in an ERD represents a real-world object or concept, such as a person, place, or thing.
What is a relationship in an ERD?
A relationship in an ERD describes how entities are related to each other within a database.
What are the three main components of an ERD?
The three main components of an ERD are entities, attributes, and relationships.
True or False: An ERD is used to design the physical layout of a database.
False
What is cardinality in an ERD?
Cardinality in an ERD defines the maximum number of times an instance in one entity can be associated with instances in another entity.
What symbol is used to represent an entity in an ERD?
A rectangle
What symbol is used to represent a relationship in an ERD?
A diamond
What symbol is used to represent an attribute in an ERD?
An oval
What is a weak entity in an ERD?
A weak entity in an ERD does not have a primary key attribute of its own and relies on the relationship with another entity for identification.
What is a composite attribute in an ERD?
A composite attribute in an ERD is an attribute that can be divided into smaller, more basic attributes.
What is an associative entity in an ERD?
An associative entity in an ERD is an entity that exists to represent a many-to-many relationship between two other entities.
What is a recursive relationship in an ERD?
A recursive relationship in an ERD occurs when an entity is related to itself.
What is an ERD cardinality of ‘one-to-one’?
An ERD cardinality of ‘one-to-one’ means that each instance of one entity is associated with exactly one instance of another entity.
What is an ERD cardinality of ‘one-to-many’?
An ERD cardinality of ‘one-to-many’ means that each instance of one entity can be associated with multiple instances of another entity.