What does a data model consist of?

The data model contents include three parts: data structure , data manipulation, and data constraints.

①Data structure: The data structure in the data model mainly describes the type, content, and nature of the data, as well as the connection between the data. Data structure is the basis of the data model, data operations and constraints are built on the data structure. Different data structures have different operations and constraints.

② data operations: data operations in the data model mainly describes the type of operation and operation mode on the corresponding data structure.

③ Data constraints: data constraints in the data model mainly describe the syntactic and lexical links between data within the data structure, the constraints and dependencies between them, and the rules for dynamic changes in data to ensure that the data is correct, valid and compatible.

Introduction

There are three basic data models that have arisen during the development of data, which are the hierarchical model, the mesh model, and the relational model. These three models are named according to their data structure. The first two use a formatted structure. In this type of structure entities are represented by record types which are abstracted as vertices of a graph. The links between record types are abstracted as connection arcs between vertices.

The entire data structure corresponds to a graph. The basic structure of the hierarchical model is a tree structure; the basic structure of the mesh model is an undirected graph without any constraints. The relational model is a non-formatted structure, with a single two-dimensional table structure to represent the entities and the links between the entities, and the relational model is the data model commonly used in databases today.