The quest for better data management has led to several models that attempt to resolve the file system’s critical shortcomings. These models represent schools of thought as to what a database is, what it should do, the types of structures that it should employ, and the technology that would be used to implement these structures. … Read more
A business rule is a brief, precise, and unambiguous description of a policy, procedure, or principle within a specific organization. In a sense, business rules are misnamed: they apply to any organization, large or small—a business, a government unit, a religious group, or a research laboratory—that stores and uses data to generate information. Business rules, … Read more
The basic building blocks of all data models are entities, attributes, relationships, and constraints. An entity is anything (a person, a place, a thing, or an event) about which data are to be collected and stored. An entity represents a particular type of object in the real world. Because an entity represents a particular type … Read more
The importance of data modeling cannot be overstated. Data constitute the most basic information units employed by a system. Applications are created to manage data and to help transform data into information. But data are viewed in different ways by different people. For example, contrast the (data) view of a company manager with that of … Read more
Database design focuses on how the database structure will be used to store and manage end-user data. Data modeling, the first step in designing a database, refers to the process of creating a specific data model for a determined problem domain. (A problem domain is a clearly defined area within the real-world environment, with well-defined … Read more
The introduction of a database system over the file system provides a framework in which strict procedures and standards can be enforced. Consequently, the role of the human component changes from an emphasis on programming (in the file system) to a focus on the broader aspects of managing the organization’s data resources and on the … Read more
While a spreadsheet allows for the creation of multiple tables, it does not support even the most basic database functionality such as support for self-documentation through metadata, enforcement of data types or domains to ensure consistency of data within a column, defined relationships among tables, or constraints to ensure consistency of data across related tables. … Read more
A DBMS performs several important functions that guarantee the integrity and consistency of the data in the database. Most of those functions are transparent to end users, and most can be achieved only through the use of a DBMS. They include data dictionary management, data storage management, data transformation and presentation, security management, multiuser access … Read more
The term database system refers to an organization of components that define and regulate the collection, storage, management, and use of data within a database environment Five components of database system Hardware. Hardware refers to all of the system’s physical devices; for example, computers (PCs, workstations, servers, and supercomputers), storage devices, printers, network devices (hubs, … Read more
Data redundancy exists when the same data are stored unnecessarily at different places. Uncontrolled data redundancy sets the stage for: Poor data security. Having multiple copies of data increases the chances for a copy of the data to be susceptible to unauthorized access. Chapter 15, Database Administration and Security, explores the issues and techniques associated … Read more