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This article is about what the data model reflects in the database. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

The data model reflects the relationship between the data of things themselves and related things. Data model is used to describe data, organize data and operate on data. It is a description of the characteristics of real-world data. The purpose of establishing the data model: the computer can not deal with the real things directly. Only when people convert the real things into digital data, can the computer recognize and process them.

The operating environment of this tutorial: windows7 system, Dell G3 computer.

Data model (Data Model) is the abstraction of data characteristics, which is used to describe data, organize data and manipulate data. It is the description of real-world data characteristics.

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 purpose of establishing the data model: the computer can not deal with the real things directly, so only when people convert the real things into digital data can the computer recognize and process them.

Constituent elements

The content described by the data model has three parts, namely data structure, data operation and data constraint.

① data structure: the data structure in the data model mainly describes the type, content, nature and relationship of the data. Data structure is the foundation of data model, and data operations and constraints are based on data structure. Different data structures have different operations and constraints.

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

③ data constraints: data constraints in the data model mainly describe the syntax, semantic relationships, constraints and dependencies between data within the data structure, as well as rules for dynamic changes of data, in order to ensure that the data is correct, effective and compatible.

Hierarchical type

Data models are divided into three types according to different application levels: conceptual data model, logical data model and physical data model.

Conceptual data Model (Conceptual Data Model) is a user-oriented and objective-world-oriented model, which is mainly used to describe the conceptual structure of the world. In the initial stage of design, database designers get rid of the specific technical problems of computer system and DBMS, concentrate on analyzing data and the relationship between data, etc., and have nothing to do with the specific data management system (Database Management System, referred to as DBMS). The conceptual data model must be replaced with a logical data model before it can be implemented in DBMS.

Logical data model (Logical Data Model) is a database system-oriented model, which is supported by specific DBMS data models, such as mesh data model (Network Data Model), hierarchical data model (Hierarchical Data Model) and so on. This model is not only user-oriented, but also system-oriented, and is mainly used in the implementation of database management system (DBMS).

Physical data Model (Physical Data Model) is a model oriented to computer physical representation, which describes the organizational structure of data on the storage medium. It is not only related to the specific DBMS, but also related to the operating system and hardware. Each logical data model has its corresponding physical data model when it is implemented. In order to ensure the independence and portability of DBMS, most of the physical data models are implemented automatically by the system, while designers only design special structures such as index, aggregation and so on.

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