Entity Relationship Diagram

1. Entity Relationship
Diagram

2. Outine
• Characteristics of E-R Model
• Components of E-R Model
• Example of E-R Model
• Enhanced E-R Model

3. E-R Model/ ERD
• A type of flowchart that illustrates how “entities” such as
people, objects or concepts relate to each other within a system.
• ER Diagrams are most often used to design or debug relational
databases in the fields of software engineering, business
information systems, education and research.
• Also known as ERDs or ER Models, they use a defined set of
symbols such as rectangles, diamonds, ovals and connecting
lines to depict the interconnectedness of entities, relationships
and their attributes.

4. Characteristics of E-R Model
• Semantic data model
• Express the logical properties of an enterprise database
• Design tools and documentation for data base structure
• No physical DBMS
• Proposed by Dr. Peter Chen
• Unified Modeling Language (UML)

5. Components of E-R Model
• Entity
• Attribute
• Key
• Relationship
• Structural constraints on relationship

6. Entity
• Definition
• An object or concept
• Types
• Strong entity (parent, owner, dominant)
• Weak entity (child, dependent, or subordinate)
• Diagram Notation
• Rectangular

7. Attribute
• Types
• Single
• Composite
• Single-valued
• Multi-valued
• Derived

8. Keys
• Candidate key
• Primary key
• Composite key

9. Relationship
• Definition
• Association among entities
• Diagram Notation
• Line – (relation or role name)
• Degree of a relationship
• Number of participating entities
• Types
• Unary (recursive relationship)
• Binary
• Ternary
• Quaternary

10. Structural Constraints on Relationship
• Cardinality constraints
• Zero-to-one 0..1
• Zero-to-many 0..*
• One-to-many 1..*
• Many-to-many *..*
• Participation constraints
• Total (mandatory, every one involved)
• Partial (optional, only some involved)
• Improper relationship
• Fan trap (ambiguous pathway)
• Chasm trap (missing pathway)

12. THANK YOU