Chapter 1: Database Systems
• Data are raw facts. Information is the result of processing data to reveal their meaning. Accurate, relavant and timely information is the key to good decision making and good decision making is the key to organizational survival in a global environment
• Data are usually stored in a database. To implement a database and manage its contents you need a database management system (DBMS). DBMS serves as an intermediary between the user and the database. The database contains the data you have collected & “data about data” metadata.
• Database design defines the database structure. A well-designed database facilitates data management and generates accurate and valuable information. A poorly designed database can lead to bad decision making and bad decision making can lead to the failure of an organization.
• Databases can be classified according to the number of users supported, where the data are located, the type of data stored, the intended data usage and the degree to which the data are structured.
• Databases evolved from manual and then computerized file systems. In a file system, data are stored in independent files, each requiring its own data management programs. Although this method of data management is largely out-moded, understanding its characteristics makes database design easier to comprehend.
• Some limitations of file system data management are that it requires extensive programming, system administration can be complex and difficult, making changes to existing structures is difficult and security features are likely to be inadequate. Also, independent files tend to contain redundant data, leading to problems of structural and data dependence.
• Database management systems were developed to address the file system’s inherent weaknesses. Rather than depositing data in independent files, a DBMS presents the database to the end user as a single data repository. This arrangement promotes data sharing, thus eliminating the potential problem of islands of information. In addition, the DBMS enforces data integrity, eliminates redundancy, and promotes data security.
1. define each of the following terms:
A) DATA: raw facts such as telephone number, birth date, customer name. Data have little meaning unless they have been organized in some logical manner. B) FIELD: a character or group of characters (alphabetic or numeric) that has a specific meaning. a field is used to define and store data. C) RECORD: a logically connected set of one or more fields that describes a person, place, or thing. For eg. The fields that constitute a customer record might consist of the customer’s name, address, phone number, date of birth, credit limit and unpaid balance. D) FILE: A collection of related records. For example, a file might contain data about the students currently enrolled at Bond University.
2. What is Data redundancy, and which characteristics of the file system can lead to it? Data redundancy is when the same data are stored unnecessarily at different places. Poor data security, data inconsistency, data anomalies (when not all the required changes in the redundant data rare made successfully).
3. What is data independence and why is it lacking in the file systems? Data independence exists when you can change the data storage characteristics without affecting the program’s ability to access the data. Lacking in the file system as most data relies on other data
4. What is a DBMS and what are its functions?
A database management system (DBMS) is a collection of programs that manages the database structure and controls access to the data stored in the database. In a sense, a database resembles a very well organized electronic filing cabinet in which powerful software (the DBMS) helps manage the cabinet’s contents. DBMS functions include data...
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