Lesson 4: Database Analysis and Design
A diagram that represents relationships among entities in a database..
Entity Relationship Diagram
3 Principal Components of ER Diagram
Entities
Attributes
Relationships
Represents the structure of the database with the help of a diagram.
Entity Relationship Model
A systematic process to design a database as it would require you to analyze all data requirements before implementing your database.
ER Modelling
He proposed ER Diagrams in 1971 to create a uniform convention that can be used as a conceptual modeling tool.
Peter Chan
He offered the data structure diagrams that also inspired his model.
Charles Bachman
Symbols Used in ER Diagrams:
It represents entity types
Rectangle
Symbol Used in ER Diagram:
Represents attributes
Ellipses
Symbol Used in ER Diagram:
Represents relationship types
Diamonds
Symbol Used in ER Diagram:
It links attributes to entity types and entity types with other relationship types
Lines
Symbol Used in ER Diagram:
It underlines the attributes
Primary Key
Symbol Used in ER Diagram:
Represents multi-valued attributes
Double Ellipses
Type of Entity
Weak Entity
Type of Attributes
Key Attribute
Composite Attribute
Multivalued Attribute
Derived Attribute
Type of Relationships
One-to-Many
One-to-One
Many-to-One
Many-to-Many