Database Structure Design Summary (2)

Theories and Methods of Database Design
1 Database Design Overview
Database is the latest technology in data management, with Data structuring, minimum redundancy, and high Program Data independence, scalability, and ease of compiling applications. So-called Database
It refers to an organized and shareable data set that is stored in a computer for a long time. [Wang Shan, Chen Hong. tutorial on database system principles. Beijing: Tsinghua University Press,
1998.7] the data in the database is organized, described, and stored according to a certain data model. It has a small degree of redundancy, high data independence and scalability, and can be shared with various users. The database application has
More and more widely, not only large computers, small and medium-sized computers, but even micro-computers use advanced database technology to maintain the integrity, integrity, and sharing of system data.
Database Design is the process of converting business objects into database objects such as tables and views. [Ryan K. Stephen, Ronald
R. plew. Database Design. Macmillan computer publishing U. S.,
2001] database design is the primary and basic content in the development of database application systems. Databases are the core and foundation of information systems. It organizes a large amount of data in the information system according to a certain model,
It provides the function of storing, maintaining, and retrieving data. It is convenient, timely, and accurate for the information system to obtain the required information from the database. Whether all parts of an information system can be closely combined and how to combine them,
The key lies in the database. Therefore, the database must be properly designed.
According to the standard design method, the whole process of database and its application system development is considered. The database design is divided into the following six stages:
(1) Demand Analysis
(2) Conceptual Structure Design
(3) Logical Structure Design
(4) Physical Mechanism Design
(5) database implementation
(6) Database Operation and Maintenance
2. Database Requirement Analysis
The entire database design must accurately understand and analyze user needs (including data and processing ). Requirement analysis is the foundation of the entire design process and the most difficult and time-consuming step. Whether the demand analysis as a foundation is fully and accurate determines the speed and quality of building a database building on it.
The task of requirement analysis is to fully understand the work of the original system (manual system or computer system) by investigating in detail the objects to be processed in the real world (organizations, departments, enterprises, etc, clarify the various requirements of users, and then determine the functions of the new system.
The focus of the demand analysis survey is "data" and "processing". Through investigation, collection, and analysis, the following database requirements are obtained:
(1) Information requirements. The content and nature of the information that the user needs to obtain from the database. Data requirements can be exported based on information requirements, that is, the data to be stored in the database.
(2) handling requirements. The processing function that the user needs to complete. Determine the user's requirements for data processing to determine the relationship between data.
(3) security and integrity requirements.
3. Database Conceptual Structure Design
Conceptual Structure Design is the process of abstracting the user requirements obtained from analysis into a conceptual model. That is, on the basis of requirement analysis, design various entities that can meet user needs and the Conceptual Structure Design Models of the relationships between them. In this way, a DBMS can be used to meet these requirements better and more accurately. It is the key to the entire database design.
The main feature of the conceptual structure is that it can reflect the real world in a real and fully; it is easy to understand; it is easy to change; it is easy to convert to various data models such as relational, mesh, and hierarchy. A powerful tool to describe the conceptual model is the E-R model.
There are four methods to design the conceptual structure:
(1) Top-down. That is, first define the framework of the global conceptual structure, and then gradually refine it;
(2) bottom-up. First, define the conceptual structures of each local application, and then integrate them to obtain a global conceptual structure;
(3) Gradually expand. First, define the most important core concept structure, then expand outward, and gradually generate other conceptual structures in the form of Snowball until the overall conceptual structure;
(4) hybrid policy. It combines top-down and bottom-up to design a global conceptual structure framework with a top-down policy, use it as the skeleton to integrate the local conceptual structures designed by the bottom-up policy. Where
The most commonly used policy is the bottom-up method. That is, perform demand analysis from top to bottom, and then design the conceptual structure from bottom to bottom. [Saradb for saradb, Wang Shan. Introduction to database systems (3rd ).
Beijing: Higher Education Press, 2003]
4. Database Logical Structure Design
A conceptual structure is an information structure independent of any data model. The task of logical structure design is to convert the basic E-R diagram designed at the conceptual structure design stage into a logical structure that is consistent with the data model supported by the selection of DBMS products.
The logical structure is generally designed in three steps:
(1) converting the conceptual structure into general relationships, networks, and hierarchical models;
(2) convert the converted relationship, mesh, and hierarchical model to the data model supported by a specific DBMS;
(3) Optimize the data model. [Abraham silberschatz, Henry F. korth, S. sudarshan.
Database System Concepts, fourth edition. McGraw-Hill Companies, Inc,
2002]
The conceptual structure and logical structure design of databases are the two most important links in the design process.
5 database Physical Structure Design
The storage structure and method of a database on physical devices are called the physical structure of a database. It depends on a given computer system. The physical design of the database is the process of selecting the physical results that best suit the application requirements for a given Logical Data Model.
The physical structure design of databases is generally divided into two steps:
(1) determine the physical structure of the database. In relational databases, it mainly refers to the access method and storage structure;
(2) evaluate the physical structure, focusing on time and space efficiency.
6. database implementation, operation and maintenance
After the physical design of the database is completed, the designer must use the data definition language provided by RDBMS and other user programs to strictly describe the database logic design and physical design results and become acceptable to the DBMS. Source code Then, the target mode is generated after debugging, and the data can be organized into the database.