What
ERD stands for Entity Relationship Diagram, a structural diagram that contains symbols nad connectors that visualizes 2 types of information
- The major Entities
- The Relationship between those entities
When we talk bout Entities, we are referring to the business objects within the system: people/role, tangile object (product).
When we talk about Relationship, we are referring how those entities relate with each other.
Primary key & foreign key
- Primary key: Use to uniquely define a record in database table
- Foreign key: a foreign key of a table is used aas a navigation to a primary key of another table
When
ERDs are mostly developed during concept visualization, database design, database debugging, requirement information system.
How-to
- Answer the purpose: What is this ERD for
- Clarify the model scope. This prevents the model from having too many redundant entities. Onyl select the entities that is critical and relevant to the business model.
- Define the models/ major entities
- Define the attribute of that entities (related information)
- Decide the relationship between those entities (which one might affect one another)
- Decide the kind of relationship
- 1:1
- 1:many
- many:1
- many:many
