Access 2002 Tutorial Revised Edition

Author: Chief Editor: Wang Lei
Publisher:
Publish Date: 2001-11-02
Features: Brief Introduction Access is a powerful and popular relational database developed by Microsoft. This book introduces the Chinese version of Access97, with its main content including database creation, basic operations on databases and tables, data queries, form design, report creation, and integration of Access97 with other applications, Access97 applications on the Internet, customizing the desktop, macros, etc. The book is suitable as a reference for computer operators and can also serve as a textbook for various training classes.
Excerpt: Chapter 1 Introduction to Chinese Access97
1.1 What is Access? Simply put, Access is a relational desktop database management system. There are three key points here: database management system, desktop, and relational. Data is the carrier of information. Through the collection and organization of data, people obtain information from the outside world, form an understanding of the world, and use this understanding to guide their actions. As early as ancient times, humans had primitive data processing activities like counting knots and stacking stones. With social development, the amount of data that needs to be processed has become increasingly large, and data processing work has also become more demanding. The emergence of computers has provided a powerful tool for data processing. The development of computer data processing technology has gone through three stages.
(1) Program Management Method This is the initial stage of data processing using computers. Programmers need to fully consider the logical and physical organization of data, and programs and data are mixed together. Its characteristics are: data cannot be stored long-term, it is attached to applications, lacks independence, and has a large amount of data redundancy.
(2) File System Method This method organizes data into data files in a certain format, separates them from applications, and stores them independently on external storage media. Applications use the file management system to create, read, and store data files. Compared to the previous method of data processing, its improvements lie in the fact that programmers no longer need to consider the details of data physical storage, allowing them to focus on logical structures and other characteristics. This method is still widely used today. However, it still has shortcomings: due to the limitations of file formats, a single data file can only correspond to one or a few applications; there is a high degree of data redundancy, and files are difficult to expand.
(3) Database Management Method The database method developed from the file system method. A database refers to a collection of all relevant data stored in computer storage media. The basic idea of the database management method is to implement centralized and unified management of all data, making data independent of programs and available for sharing by various users to reduce data redundancy due to non-sharing. A database management system (DBMS) refers to the functional module that uniformly manages and controls data resources in a database. It is the core part of the database system, providing an interface between users and data. To effectively describe objective entities, the method of establishing a data model is used. A data model refers to a set of data objects and their relationships. Data models can be divided into three main categories: hierarchical model, network model, and relational model.
(1) Hierarchical Model The hierarchical model uses an inverted tree to represent the relationship between data objects. An upper node can be linked to multiple lower nodes, while any lower node can only be connected to one upper node. As shown in Figure 1-1. This model can express some facts, but because of its strict hierarchical limitations, it is not flexible enough to express the complex and changing relationships between objective entities.
(2) Network Model The network model uses the network-like relationships between data objects to describe the real world. As shown in Figure 1-2. The network model can describe the relationships between data objects more flexibly, but it has shortcomings such as complex structure.
(3) Relational Model In the relational model, the relationships between different data elements are represented by relationships. The logical structure of the data is converted into a two-dimensional table form that meets certain conditions. As shown in Figure 1-3.