How are database types classified?

Database types are divided according to data models. Data Model (Data Model) is an abstraction of data characteristics.

Data (Data) is a symbolic record that describes things, and model (Model) is an abstraction of the real world. (Recommended learning: MySQL Video Tutorial)

The data model describes the static characteristics, dynamic behavior and constraints of the system from an abstract level, providing an information representation and operation for the database system. Abstract frame. The content described by the data model has three parts: data structure, data operations and data constraints.

The content described by the data model includes three parts: data structure, data operations, and data constraints.

1) Data structure: It mainly describes the type, content, nature and relationship between data, etc. It is a collection of target types.

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

Data types such as record types and data items in the DBTG (Database Task Group) network model, relationships and domains in the relational model, etc. The contact part includes the line types in the DBTG network model, etc. Data structure is the basis of data model, and data operations and constraints are basically based on data structure. Different data structures have different operations and constraints.

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

3) Data constraints: Data constraints in the data model mainly describe the syntax and word meaning connections between data in the data structure, the constraints and dependencies between them, and the rules for dynamic changes in data to ensure the stability of the data. Correct, valid and compatible. It is a collection of integrity rules to limit the database state and state changes that conform to the data model.

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

Three basic data models have been produced during the data development process, which are hierarchical model, network model and relational model.

These three models are named according to their data structures. The first two use formatted structures. In this type of structure, entities are represented by records, and records are abstracted as vertices of the graph.

The connection between record types is abstracted as the connection arc between vertices. The entire data structure corresponds to the graph. The basic structure of the hierarchical model is a tree structure; the basic structure of the network model is an undirected graph without any restrictions. The relational model is an unformatted structure that uses a single two-dimensional table structure to represent entities and the relationships between entities.

The most widely used is the relational model. Among the logical data types, the most commonly used ones are hierarchical model, network model and relational model.

For more MySQL related technical articles, please visit the MySQL Tutorial column to learn!

The above is the detailed content of How are database types classified?. For more information, please follow other related articles on the PHP Chinese website!