The database is established based on the "data model". The data model is a simulation and abstraction of real-world data characteristics. It describes the static characteristics, dynamic behavior and constraints of the system from an abstract level, and provides an abstract framework for the information representation and operation of the database system.
The operating environment of this tutorial: Windows 7 system, Dell G3 computer.
The database is established based on the "data model".
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Model can reveal the essential characteristics of things more vividly and intuitively, allowing people to have a more comprehensive understanding of things , in-depth understanding, which can help people solve problems better. Using models to describe things is a method widely used by people in the process of understanding and transforming the world. Computers cannot directly process objective things in the real world, and database systems use computer technology to manage objective things. Therefore, it is necessary to abstract and simulate objective things to establish a data model suitable for database system management. A data model is a simulation and abstraction of real-world data characteristics.
The data model is a tool used in database design to abstract the real world. It is a formal framework used in the database to provide information representation and operation methods. The data model is the core and foundation of the database system.
Components:
The content described by the data model includes three parts: data structure, data operations, and data constraints.
①Data structure: The data structure in the data model mainly describes the type, content, nature of data and the relationship between data. Data structure is the basis of data model, and data operations and constraints are based on data structure. Different data structures have different operations and constraints.
②Data operations: Data operations in the data model mainly describe the operation types and operation methods on the corresponding data structure.
③Data 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 accuracy of the data. , effective and compatible.
Data model classification:
1. Hierarchical model: organizes data into a one-to-many relationship structure, and uses a tree structure to represent entities and the relationships between entities.
2. Network model: Use connection instructions or pointers to determine the network connection relationship between data. It is a many-to-many data organization method.
3. Relational model: Organize data in the form of record groups or data tables to facilitate storage and transformation using the relationships between various entities and attributes. There is no hierarchy or pointers. It is a way to establish spatial data. A very effective data organization method for relationships between attribute data.
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