3.2 Database Architecture: Database Design Process, Requirements Analysis, Conceptual Structure Design, Logical Structure Design, Physical Design
database architecture
demand analysis
First of all, before doing the corresponding database design, you first need to know what to design, so you must first do a demand analysis. Second, this demand analysis refers to data-related needs. You need to consider the data needs of current and future applications, and consider the relevant requirements of data processing. .
Dial-in In recent years, social security cards, ID cards, and one-card cards have become very popular in hospitals, but when you went to the hospital five years ago, you didn’t bring these things with you. When you registered user information at that time, some cities might not To register these fields, cities that are more open will make records first, but there is no need to put this redundant field first, and go back and consider some requirements used by Ken at that time and in the future for design.
After completing the requirements analysis, some products will be obtained. The requirements analysis products of database design also include data flow diagrams, data dictionaries, and requirements specifications .
Data flow diagrams and data dictionaries are generally used in combination. The data flow graph represents the process of data conversion and transformation in the form of a graph, and the detailed meaning of some data is described in detail in the data dictionary. The two are generally used in combination, and at the same time, the requirements will be explained to obtain a requirements specification.
After knowing what to do, the following is the conceptual structure design.
conceptual structure design
The conceptual structure design refers to the product of the requirement specification, and also considers the application requirements in the data. The conceptual design is an abstraction of the real world, and what is obtained is a conceptual model. The conceptual model mentioned in the database actually refers to the ER diagram. , also known as an entity-relationship diagram.
In the conceptual structure design stage, the database management system was not considered during the processing process. It has nothing to do with the database management system, that is, it has nothing to do with the DBMS. No matter it is MySQL, Oracle, etc., no matter what it is, during the design process, the concept The structure design stage is just to abstract the corresponding data into the form of ER diagram for the real world.
After getting the ER diagram, the next step is to enter the logical structure design.
logical structure design
In the design phase of logical structure design, while considering the requirements, it also considers the conversion of ER diagrams into logical structure diagrams. The logical structure corresponds to the data model. In a relational database, the model schema involved is a relational schema.
Logical structure design is based on requirements, ER diagrams, conversion rules from ER diagrams to logical structures, and standardization theories.
A relational schema can also be called a relational table, and the basic tables we usually refer to are built with reference to the relational schema.
When considering the relational model, the characteristics of the database system (DBMS) to be selected will also be considered.
physical design
In the physical design stage, the main task is to design the corresponding distribution form, storage form, and some access forms of the database, and some characteristics of the hardware and operating system need to be considered. Generally speaking, indexes are involved in the exam, especially clustered indexes, which will modify the specific physical structure order, and indexes are the main considerations in the physical design stage.
Combined with the previous three-level internal and external modes, the index belongs to the internal mode and belongs to the file level.
ER model or ER diagram is quite special. In the information system life cycle, it is a product of system analysis data modeling. In database structure design, it is a product of the conceptual structure design stage. information systems, or database design.