Isys104 Tutorial – Week 7

Topics: Database, SQL, Database management system Pages: 11 (3300 words) Published: April 2, 2013
ISYS104 Tutorial – week 7

Review Questions

1. What are the problems of managing data resources in a traditional file environment and how are they solved by a database management system?

List and describe each of the components in the data hierarchy.

Figure 6–1 shows the data hierarchy. The data hierarchy includes bits, bytes, fields, records, files, and databases. Data are organized in a hierarchy that starts with the bit, which is represented by either a 0 (off) or a 1 (on). Bits can be grouped to form a byte to represent one character, number, or symbol. Bytes can be grouped to form a field, such as a name or date, and related fields can be grouped to form a record. Related records can be collected to form files, and related files can be organized into a database.

Define and explain the significance of entities, attributes, and key fields.

• Entity is a person, place, thing, or event on which information can be obtained. • Attribute is a piece of information describing a particular entity. • Key field is a field in a record that uniquely identifies instances of that unique record so that it can be retrieved, updated, or sorted. For example, a person’s name cannot be a key because there can be another person with the same name, whereas a social security number is unique. Also a product name may not be unique but a product number can be designed to be unique.

List and describe the problems of the traditional file environment.

Problems with the traditional file environment include data redundancy and confusion, program-data dependence, lack of flexibility, poor security, and lack of data sharing and availability. Data redundancy is the presence of duplicate data in multiple data files. In this situation, confusion results because the data can have different meanings in different files. Program-data dependence is the tight relationship between data stored in files and the specific programs required to update and maintain those files. This dependency is very inefficient, resulting in the need to make changes in many programs when a common piece of data, such as the zip code size, changes. Lack of flexibility refers to the fact that it is very difficult to create new reports from data when needed. Ad-hoc reports are impossible to generate; a new report could require several weeks of work by more than one programmer and the creation of intermediate files to combine data from disparate files. Poor security results from the lack of control over the data because the data are so widespread. Data sharing is virtually impossible because it is distributed in so many different files around the organization.

Define a database and a database management system and describe how it solves the problems of a traditional file environment.

A database is a collection of data organized to service many applications efficiently by storing and managing data so that they appear to be in one location. It also minimizes redundant data. A database management system (DBMS) is special software that permits an organization to centralize data, manage them efficiently, and provide access to the stored data by application programs.

A DBMS can reduce the complexity of the information systems environment, reduce data redundancy and inconsistency, eliminate data confusion, create program-data independence, reduce program development and maintenance costs, enhance flexibility, enable the ad hoc retrieval of information, improve access and availability of information, and allow for the centralized management of data, their use, and security.

2. What are the major capabilities of DBMS and why is a relational DBMS so powerful?

Name and briefly describe the capabilities of a DBMS.

A DBMS includes capabilities and tools for organizing, managing, and accessing the data in the database. The principal capabilities of a DBMS include data definition language, data dictionary, and...
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