Isys104 Tutorial – Week 7
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
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