Introduction to Entity Relationship Diagrams.
Entity-Relationship Diagrams (ERDs) provide a visual representation of the database structure.
They facilitate communication among stakeholders, guide the database design process, and serve as documentation for the database schema.
Entity Relationship Diagram (ERD)
Types of Entity Relationship Diagrams
There are three types of Entity Relationship Diagrams - Conceptual, Logical & Physical.
As the project progresses and requirements became more defined the ERDs needed will move from Conceptual through to Physical.
Which ERD type is closest to the actual database implementation?
Conceptual ERD (CERD)
Focuses on high-level relationships between entities.
Used in the initial stages of database design to capture essential entities and their relationships.
Helps stakeholders understand the scope and requirements of the database system.
Used by: Business analysts, stakeholders, project managers
Example Conceptual Entity Relationship Diagram
An entity in an ER diagram is represented by a
.
A relationship in an ERD is represented by a/an
connecting two entities.
Logical Entity Relationship Diagrams
Used to translate the conceptual model into a relational database schema.
Specifies attributes for each entity, defines cardinality (one to one, one to many) and participation(optional vs required) constraints.
Provides a detailed view of the database schema, including primary and foreign keys.
Used by: Database designers, data architects, developers
What is an attribute in an Entity Relationship Diagram?
Example Logical Entity Relationship Diagram
A Logical ERD focuses on the relationships between entities using
to connect them.
Physical Entity Relationship Diagrams
Represents the actual implementation of the database on a specific DBMS in order to to build, optimize, and maintain the physical database schema.
Includes details such as data types, indexes, storage options, and constraints tailored to the chosen DBMS.
Used by database administrators, system administrators, developers.
In a Physical ERD, the actual data types and lengths of attributes are specified according to the chosen
.
Example Physical Entity Relationship Diagram
What is cardinality in an Entity Relationship Diagram?
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