We have not yet understood the three concepts of databases. Today, I am here to answer your questions, improve them together, and combine them with our daily understanding.
Conceptual Model
Conceptual ModelAfter understanding the user's needs and work conditions in the user's business field, the author analyzes and summarizes some concepts used to describe the user's business needs. For example, in the sales business, there are "customers" and "orders", and "goods" and "sales personnel ".
Use Case (use case diagram) describes the situation: "clerk" and "customer" sign an "order" when purchasing "goods ".
Logical Model (relational model)
Logical Model It is necessary to detail the conceptual model. To implement what is described in a conceptual model, you must provide detailed functions and process detailed information. This is the refined stage of demand analysis.
Take the sales business as an example: the "customer" information should basically include the organization name, contact person, contact phone number, address, and other attributes; the "product" information should basically include: name, type, type, unit price, and other attributes; "order" information should basically include: Date and Time attributes. The "order" must be associated with the "customer", "salesman", and "commodity" details.
The system needs to create several data tables: salesman information table, customer information table, commodity information table, and order table.
The system includes several functions: salesman information maintenance, customer information maintenance, commodity information maintenance, and creation of sales orders.
All of the above are logical models. The descriptions only indicate what the system is to implement, but there is no tool for implementation. The latter is within the scope of the physical model.
Physical Model
Physical Model It is implemented on detailed physical media based on the above logic model. For example, if the database uses sqlserver2008, you can write detailed SQL scripts to create the database on the database server. Contains the salesman information table, customer information table, product information table, and order table. When the client uses vs2012 development tools, VS is used on the workstation to create a function menu, including salesman information maintenance, customer information maintenance, product information maintenance, and creation of sales orders, use tools to encode each function.
Summary
These three processes are three key steps for implementing a software system. They are a process from abstraction to detail for continuous and well-refined analysis, design, and development, combining powerdesigner with analysis, design, and database tables is the entire process of understanding. The content of learning this part should be related to our actual learning. Although it is abstract, however, they are often used in connection with life, which is not so unfamiliar. This is also the advantage of learning connection. learning is not messy. The more information is learned, the more network learning is compiled, and there is no place in life.
Road to soft test (4) --- Software Project 1 Conceptual Model, logical model, physical model
