Isys104 Tutorial – Week 7

3285 Words Mar 19th, 2013 14 Pages
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,
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• The data dictionary is an automated or manual file that stores information about the data in the database, including names, definitions, formats, and descriptions of data elements. • The data manipulation language, such as SQL, is a specialized language for accessing and manipulating the data in the database.

Define a relational DBMS and explain how it organizes data.

The relational database is the primary method for organizing and maintaining data today in information systems. It organizes data in two-dimensional tables with rows and columns called relations. Each table contains data about an entity and its attributes. Each row represents a record and each column represents an attribute or field. Each table also contains a key field to uniquely identify each record for retrieval or manipulation.

List and describe the three operations of a relational DBMS.

In a relational database, three basic operations are used to develop useful sets of data: select, project, and join. • Select operation creates a subset consisting of all records in the file that meet stated criteria. In other words, select creates a subset of rows that meet certain criteria. • Join operation combines relational tables to provide the user with more information that is available in individual tables. • Project operation creates a subset consisting of columns in a table, permitting the user to create new tables that contain only

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