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This article mainly introduces how the database type is divided, has a certain reference value, friends in need can refer to. I hope you will learn a lot after reading this article. Next, let the editor take you to learn about it.

Database types are divided according to the data model, and the data model (Data Model) is the abstraction of data features.

Data (Data) is a symbolic record that describes things, and Model (model) is an abstraction of the real world. (recommended study: MySQL video tutorial)

The data model describes the static characteristics, dynamic behavior and constraints of the system from the abstract level, and provides an abstract framework for the information representation and operation of the database system. The data model describes three parts: data structure, data operation and data constraint.

The content described by the data model includes three parts: data structure, data operation and data constraint.

1) data structure: it mainly describes the type, content, nature and relationship of data, which is a collection of target types.

The target type is the component of the database, which can be divided into two categories: data type and the relationship between data types.

Data types such as records, data items in DBTG (database task group) mesh model, relationships and domains in relational model, etc. The connection part includes the system type of DBTG mesh model and so on. Data structure is the foundation of data model, and data operations and constraints are basically based on data structure. Different data structures have different operations and constraints.

2) data operation: the data operation in the data model mainly describes the operation type and operation mode on the corresponding data structure. It is a collection of operation operators, including several operations and inference rules, to operate on a database composed of valid instances of the target type.

3) data constraints: the data constraints in the data model mainly describe the syntax, semantic relations, constraints and dependencies among the data within the data structure, as well as the rules of dynamic changes of the data to ensure the correctness, effectiveness and compatibility of the data. It is a collection of integrity rules that define the state of the database that conforms to the data model, as well as changes in state.

According to different principles, constraints can be divided into data value constraints and data connection constraints; static constraints and dynamic constraints; entity constraints and reference constraints between entities.

According to the development process, there have been three basic data models, which are hierarchical model, mesh model and relational model.

These three models are named after their data structures. The first two adopt a formatted structure. In this kind of structure, the entity is represented by the record type, which is abstracted as the vertex of the graph.

The relationship between record types is abstracted as a connection arc between vertices. The whole data structure corresponds to the diagram. The basic structure of the hierarchical model is a tree structure, and the basic structure of the mesh model is an undirected graph without any restrictions. The relational model is an unformatted structure, and the structure of a single two-dimensional table is used to represent the relationship between entities and entities.

Among them, relational model is the most widely used, and hierarchical model, mesh model and relational model are the most commonly used in logical data types.

Thank you for reading this article carefully. I hope it will be helpful for everyone to share how the database types are divided. At the same time, I also hope you can support us, pay attention to the industry information channel, and find out if you have any problems. detailed solutions are waiting for you to learn!

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