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Questions and Answers
What is the primary purpose of an Entity Relationship Diagram (ERD)?
Which of the following is an attribute of an entity in an ERD?
What is the term for a relationship where one entity is related to only one other entity?
What notation uses rectangles for entities and lines for relationships?
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What is the first step in creating an ERD?
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Study Notes
Entity Relationship Diagram (ERD)
Definition
An Entity Relationship Diagram (ERD) is a visual representation of data entities and their relationships in a database.
Components
- Entities: Represented as rectangles, entities are objects or concepts that have attributes or properties.
- Attributes: Represented as columns, attributes are the characteristics or properties of an entity.
- Relationships: Represented as lines, relationships describe how entities interact with each other.
Types of Relationships
- One-to-One (1:1): One entity is related to only one other entity.
- One-to-Many (1:N): One entity is related to multiple entities.
- Many-to-Many (M:N): Multiple entities are related to multiple entities.
Notations
-
Chen's Notation:
- Rectangles for entities
- Lines for relationships
- Arrowheads for cardinality (1:1, 1:N, M:N)
-
Crow's Foot Notation:
- Rectangles for entities
- Lines with crow's foot symbols for relationships
- Cardinality indicated by the number of lines
Steps to Create an ERD
- Identify entities and their attributes
- Determine relationships between entities
- Choose a notation (Chen's or Crow's Foot)
- Draw the ERD diagram
Benefits
- Visualizes complex data relationships
- Helps in database design and development
- Facilitates communication among stakeholders
- Enhances data modeling and data analysis
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Description
Learn the fundamentals of creating Entity Relationship Diagrams (ERDs), including entities, attributes, and relationships. Discover the different notations and steps to create an ERD for effective database design and development.
