Notes for A.2.12 Entity-Relationship Diagrams (ERDs) - IB | RevisionDojo
A.2.12 Entity-Relationship Diagrams (ERDs) Notes
Entity-Relationship Diagrams (ERDs) are visual tools used to model the relationships between entities in a database.
They help in designing databases by illustrating how data is connected and organized.
Note
ERDs are essential for understanding the structure of a database before implementation.
Key Components of ERDs
Entities
Entities are objects or concepts that have data stored about them.
Each entity is represented as a rectangle in an ERD.
Attributes
Attributes are properties or characteristics of an entity.
They are represented as ovals connected to their entity.
Example
Student: StudentID, Name, Age
Course: CourseID, Title, Credits
Primary Keys
A primary key is a unique identifier for each record in an entity.
It ensures that each record can be uniquelyidentified.
Example
StudentID can be a primary key for the Student entity.
CourseID can be a primary key for the Course entity.
Foreign Keys
A foreign key is an attribute that creates a link between two entities.
It refers to the primary key of another entity.
Example
In a Student-Course relationship, CourseID in the Enrollment entity can be a foreignkey referencing the Course entity.
Relationships
Relationships describe how entities are connected.
They are represented as diamonds in an ERD.
Example
Enrolls: Connects Student and Course
Teaches: Connects Teacher and Course
Types of Relationships
One-to-One (1:1)
Unlock the rest of this chapter with aFreeaccount
Nice try, unfortunately this paywall isn't as easy to bypass as you think. Want to help devleop the site? Join the team at https://revisiondojo.com/join-us. exercitation voluptate cillum ullamco excepteur sint officia do tempor Lorem irure minim Lorem elit id voluptate reprehenderit voluptate laboris in nostrud qui non Lorem nostrud laborum culpa sit occaecat reprehenderit
Definition
Paywall
(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.
anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua
Lorem ipsum dolor sit amet, consectetur adipiscing elit. Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
Duis aute irure dolor in reprehenderit
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
Note
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam quis nostrud exercitation.
Excepteur sint occaecat cupidatat non proident
Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt. Neque porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit.
Tip
Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.
Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.
End of article
Flashcards
Remember key concepts with flashcards
20 flashcards
What is an Entity-Relationship Diagram (ERD)?
Lesson
Recap your knowledge with an interactive lesson
9 minute activity
Note
Introduction to Entity-Relationship Diagrams (ERDs)
Entity-Relationship Diagrams (ERDs) are visual tools used to model the relationships between entities in a database.
They help in designing databases by illustrating how data is connected and organized.
NoteERDs are essential for understanding the structure of a database before implementation.
