The Database Approach – Answers to Textbook Questions

Chapter 1 The Database approach – Answers to Textbook Questions

1.  Data: Data are raw facts. Raw facts that have not been processed to reveal its true nature. Data have little meaning unless they have been processed in a logical manner.

Field: A character or group of characters that has specific meaning.

Record: A logically connected set of one or more fields that describe a person place or thing.

File: A collection of related records.

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2. Data redundancy: When the same data is stored unnecessarily at different places. E.g. all agents’ phone number is stored in both the Customer file and Agent file.  

Data redundancy can lead to:

1. Data inconsistency: When different and conflicting versions occur of the same data in different types. Eg Wiliam in customer file and Wilfred in agent file.
2. Poor data security: Having multiple copies of data increases the chances for a copy of the data to be handled by unauthorised access.
3. Data anomalies: When all the required changes in the redundant data are not made successfully. Forcing field value changes in many different locations. E.g. when an agent gets married, she changes her surname, phone number and address. Instead of changing the fields in one file such as the agent file, you must also make changes in the customer file.  The different types of anomalies are :  update anomalies, Insertion anomalies, Deletion anomalies.

3.  Data dependence: When all data access programmes are subject to change when any of the file’s data storage is changed. Data independence: When it is  possible to make changes in the data without affecting the application programme to access the data.  

4.  DBMS: A collection of programs that manage the database structure and controls the access to the data stored in the database.

5.  Structural dependence: When access to a file is dependent on its structure. If you change the structure of your file – that is, you add a field, delete a field, and so on -- then all the programs that access that file must be changed to reflect the new structure.

6. Data: Raw facts that have not been processed to reveal its meaning.

    Information: The result of processing raw data to reveal its true meaning.

7. The DBMS acts as an intermediary between the user and the database. The database receives application requests and translates them into complex operations to fulfil those requests.  

Advantages include:

1. The database can be shared amongst multiple applications or users.
2. The databases integrates many different users.
3. Improved data sharing: End-users have better access to more well-managed data.
4. Better data integration: Wider access allows for a clearer big picture.
5. Minimised data inconsistency: When a sales agent is Bill Brown in the agents file and then shown as William Brown in the sales file.
6. Improved data access: Allows for quick answers to ad hoc “spur of the moment” queries. E.g. What is the sales amount for this month?
7. Improved decision making: Generate better quality information from which decisions are based.
8. Increased productivity: Users can make quick decisions.

8.  User classification 

1. Single-user database: Supports only one user at a time
2. Desktop database: A single-user database that runs on a PC
3. Multi-User database: Supports multiple users at the same time.
4. Workgroup Database: A multiuser database that supports small numbers < 50
5. Enterprise Database: A multiuser database that supports many users, departments > 50

Location

1. Centralised Database: A database that supports data located in a site
2. Distributed Database: A database that is distributed across several sites

Usability and time

1. Operational database: Designed to support a company’s day-to-day operations.
2. Analytical database: Storing historical and business metrics. Used exclusively for tactical and strategic decisions.
3. Data Warehouse: Storing data to generate information required for decision making.

9.  

1. Hardware: The physical components
2. Software:

1. Operating Software: Manages all hardware and makes it possible for other software to run
2. DBMS: Manages the database within the operating system.
3. Application software and utility: Used to access, manipulate and manage computer environment.  

3.  People: End-users, System Admin, Database Admin, Database d        esigner, Systems analyst.

4. Procedure: The rules and instructions of databases

5. Data: Collection of raw facts.  

10. Metadata: Data about the data

11.  Poor design → Difficult to trace errors→Bad decision making→Failure

12. Lengthy development time, difficulty getting quick answers, complex system admin- the number of files expands as each file must have its own management programme, lack of security, extensive programming – changes to file structure forces modification to all programmes that use the data → more bugs.  

Problems

1. Records = 7. There are 5 fields per record.

2. If you had a listing by city, you would experience the problem of data redundancy. There are a number of projects occurring repeatedly in Paris and London. If a there was a listing by city, you would have the same data stored unnecessarily at different places.

        Online Answer: Searching for city name within the MANAGER_ADDRESS field would be very inconvenient since the street name, city, state, and zip code are all grouped together. Altering the file structure into MANAGER_STREET, MANAGER_CITY, MANAGER_STATE, and MANAGER_ZIP would be the most practical way to produce a listing by city alone.

3.  The most efficient way would be to break down everything to its component part.  The file structure will be altered into MANAGER_LASTNAME, MANAGER_AREA CODE, MANAGER_CITY, MANAGER_COUNTRY, MANAGER_POSTECODE.

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