Advantages: E-R diagram is a powerful tool to abstract and describe the display world. The conceptual model represented by E-R diagram is independent of the data model supported by specific DBMS, and is the common foundation of various data models, so it is more general, more abstract and closer to the real world than the data model.

Disadvantages: E-R modeling also has its limitations. In E-R modeling, data and application are separated, and E-R diagram only focuses on data, which can't provide us with more information about business processes.

There are four components in the ER diagram:

Rectangular box: represents an entity, and the entity name is recorded in the box.

Diamond box: indicates the contact person, and the name of the contact person is recorded in the box.

Oval box: indicates the attribute of an entity or contact, and records the attribute name in the box. Please underline the main attribute name.

Connection: between entity and attribute; Between entity and contact; Connections and attributes are connected by a straight line, and the type of connection is marked on the straight line.

Refer to the above content: Baidu Encyclopedia -ER Diagram