Database Solutions

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DATABASE SOLUTIONS (2nd Edition)

THOMAS M CONNOLLY & CAROLYN E BEGG

SOLUTIONS TO REVIEW QUESTIONS

Chapter 1 Introduction- Review questions

1.1List four examples of database systems other than those listed in Section 1.1. Some examples could be:
A system that maintains component part details for a car manufacturer; •An advertising company keeping details of all clients and adverts placed with them; •A training company keeping course information and participants’ details; •An organization maintaining all sales order information. 1.2Discuss the meaning of each of the following terms:

(a)data
For end users, this constitutes all the different values connected with the various objects/entities that are of concern to them. (b)database
A shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization. (c)database management system
A software system that: enables users to define, create, and maintain the database and provides controlled access to this database. (d)application program
A computer program that interacts with the database by issuing an appropriate request (typically an SQL statement) to the DBMS. (e)data independence
This is essentially the separation of underlying file structures from the programs that operate on them, also called program-data independence. (f)views.
A virtual table that does not necessarily exist in the database but is generated by the DBMS from the underlying base tables whenever it’s accessed. These present only a subset of the database that is of particular interest to a user. Views can be customized, for example, field names may change, and they also provide a level of security preventing users from seeing certain data. 1.3Describe the main characteristics of the database approach. Focus is now on the data first, and then the applications. The structure of the data is now kept separate from the programs that operate on the data. This is held in the system catalog or data dictionary. Programs can now share data, which is no longer fragmented. There is also a reduction in redundancy, and achievement of program-data independence. 1.4Describe the five components of the DBMS environment and discuss how they relate to each other. (1)Hardware:The computer system(s) that the DBMS and the application programs run on. This can range from a single PC, to a single mainframe, to a network of computers. (2)Software:The DBMS software and the application programs, together with the operating system, including network software if the DBMS is being used over a network. (3)Data:The data acts as a bridge between the hardware and software components and the human components. As we’ve already said, the database contains both the operational data and the meta-data (the ‘data about data’). (4)Procedures:The instructions and rules that govern the design and use of the database. This may include instructions on how to log on to the DBMS, make backup copies of the database, and how to handle hardware or software failures. (5)People:This includes the database designers, database administrators (DBAs), application programmers, and the end-users. 1.5Describe the problems with the traditional two-tier client-server architecture and discuss how these problems were overcome with the three-tier client-server architecture. In the mid-1990s, as applications became more complex and potentially could be deployed to hundreds or thousands of end-users, the client side of this architecture gave rise to two problems: •A ‘fat’ client, requiring considerable resources on the client’s computer to run effectively (resources include disk space, RAM, and CPU power). •A significant client side administration overhead.

By 1995, a new variation of the traditional two-tier client-server model appeared to solve these problems called the three-tier client-server architecture. This new architecture proposed three...
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