The three elements of the er model

The three elements of the er model: entities, attributes, and connections. Entity is a user of data, all the characteristics in the entity are called attributes, entity will not exist alone, entity and other entities are inextricably linked.

ER Model Introduction

ER Model, also known as the Entity-Relationship Model (ERM), was proposed by Chinese-American P.S. Chen in 1976, which provides a user-oriented representation that is not constrained by any DBMS, and has been widely used as a tool for data modeling in database design, and ERM is often used in information system design to describe the information requirements and/or the type of information to be stored in a database. The ER model is commonly used in information systems design to describe information requirements and/or the type of information to be stored in a database.

Structural Classification

The components of the E-R model are entity sets, attributes, and linkage sets, which are represented as follows:

(1) Entity sets are represented by a rectangular box, with the name of the entity written inside the rectangular box.

(2) The attributes of an entity are represented by an elliptical box with the name of the attribute written inside the box and connected to its entity set with an undirected edge.

(3)

The links between entities are represented by diamond-shaped boxes, with the links named with appropriate meanings, the names written in the diamond-shaped boxes, and the rectangular boxes of entities participating in the links are connected to the diamond-shaped boxes with undirected connecting lines, respectively, with the type of the links indicated on the connecting lines, i.e., 1-1, 1-N, or M -N.