English Access 2002 Tutorial Revised Edition

Author: Chief Editor: Wang Lei
Publisher:
Publish Date: 2001-11-01
Features: Brief Introduction Access is a powerful and popular relational database developed by Microsoft. This book introduces the Chinese version of Access97, covering the main content such as creating databases, basic operations on databases and tables, data queries, designing forms, creating and designing reports, and integrating Access97 with other applications. It also includes the application of Access97 on the Internet, customizing the desktop, macros, etc. This 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 to guide their actions. As early as ancient times, humans had primitive data processing activities such as knotting and stone records. With the development of society, the amount of data to be processed has become larger and larger, and the workload of data processing has also become heavier. 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 using computers for data processing. 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, 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 create, read, and store data files through the file management system. Compared to the previous data processing method, the improvements are that programmers no longer need to consider the details of the physical storage of data, but can focus on other characteristics such as logical structure. This method is still widely used today. However, this method still has shortcomings: due to the limitations of file formats, the same 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 is developed based on the file system method. A database refers to a collection of related data stored in computer storage media. The basic idea of the database management method is to implement centralized and unified management of all data, so that data can exist independently of programs and be shared by various users, reducing data redundancy due to lack of sharing. A database management system refers to a functional module that unifies 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 things, the method of establishing a data model is adopted. A data model refers to a set of data objects and their relationships. Data models can be divided into three major 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-level node can be linked to multiple lower-level nodes, while any lower-level node can only be linked to one upper-level node. As shown in Figure 1-1. This model can describe some facts, but because of its strict hierarchical limitations, it is not flexible enough to express the complex and changing relationships between objective things.
(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 data is converted into a two-dimensional table form that meets certain conditions. As shown in Figure 1-3.