Introduction of conceptual model, logical model and physical model

A conceptual model is something that describes users' business needs after understanding their needs and their work in the business field. For example, customers and orders in sales business, as well as goods and salesmen, are described by use cases: salesmen and customers sign orders to buy goods, and the conceptual model is represented by E-R diagram, which is mainly composed of three elements: entity, attribute and connection.

Taking the first-step requirement as an example, the conceptual diagram (ER diagram):

Remarks: drawing tool draw.io

Logical model is the process of transforming conceptual model into concrete data model, that is, according to the basic E-R diagram established in the conceptual structure design stage and the data model (hierarchical/mesh/relational/object-oriented) supported by the selected management system software, it is transformed into the corresponding logical model, which should conform to the principle of relational data model;

The relationship between primary key and foreign key entities of more entities than the conceptual model.

Take the first step demand as an example, and the logic diagram is as follows:

Remarks: drawing tool draw.io

The physical model is based on the above-mentioned logical model, and it is implemented on a specific physical medium. The system needs to establish several data tables.

Take the first step demand as an example, and the logic diagram is as follows:

Remarks: drawing tool PDMan

Automatically generate table-building statements