1. What is an ER diagram?
ER diagram, also known as Entity Relationship Diagram, provides a method to represent entity types, attributes and relationships, and is used to describe the conceptual model of the real world.
2. Why draw an ER diagram?
- It is an efficient way to describe conceptual models of real-world relationships.
- It is a way of representing a conceptual relationship model.
3. How to draw an ER diagram?
- Use " rectangular box " to represent the entity type , and write the entity name in the rectangular box
- Use " elliptical frame " or rounded rectangle to represent the attributes of the entity , and use "solid line segments" to connect them with the "entity type" of the corresponding relationship.
- Use a " diamond box " to represent the cause of the connection between entity types , write the name of the connection in the diamond box, and use "solid line segments" to connect it to the relevant entity types respectively, and mark the type of connection next to the "solid line segment" (1 :1,1:n or m:n).
4. Examples
