Exercise 2:

Sample of Questions and Answer Scheme

Introduction to Geographic Information System (GIS)

Course Code: Geog 496

Instructor: Dr. M. M. Yagoub

Text Book

Burrough, P. A. and R. A. McDonnell, 1998.  Principles of Geographical Information Systems. Oxford University Press, London.

 

Refer to page:

Data types: 12-34

Database: 44-51

 

 

          Topic: Database Management System (DBMS)

 

Define  DBMS?

DBMS is a collection of data (database) and programs to access that data. The goal of DBMS is to store, retrieve, and display information (attribute).

 

Why we need database?

Without database GIS is cartography (electronic map)

No database No spatial analysis

 

What are the Key characteristics of DBMS ?

Key characteristics of DBMS are:  performance, store large volume of database, share data (access), provide security (authorization), remove redundancy (normalization) and provide concurrent access (different users at the same time).

 

List and define the main types of database models?

 

Object-based logical models: Are used to describe data at the conceptual and view level. Example of these  are the Entity-Relationship model and object-oriented model

Record-based logical models : Are used to describe data at the conceptual and view level. Example of these are: Network model, Hierarchical model, and relational model.

Physical data models: Are used to describe data at the physical level (bytes and words). It is mainly deal with hardware.

 

Define relational database?

A relational database consists of a collection of tables, each of which is assigned a unique name. A table consists of columns (fields, items) and records (row). Examples of RDBMS are Oracle, Informix, and Sybase.

 

List 3 reasons  why to use  Relational Model?

1.     Independence of the physical data storage and logical database structure.

2.     Variable and easy access to all data.

3.     Flexible in database design (simple tables and relationships)

 

Define Primary Key and Foreign Key?

 

Relational database use primary keys and foreign keys to allow mapping of information from one table to another

A foreign key is column or group of columns in a table whose value matches those of the primary key of another table

Values in primary key column must be unique e.g. social security number (SSN)

 

Make a sample tables showing the following  Relationships, illustrate by drawing table?

 

One-to-One : One customer  to one account number

One-to-Many: One Complex Building to many owners

 

Define Data Definition Language (DDL)?
 DDL store files that contains data about data (metadata). For example storage of structure in data dictionary

 

Define Data Manipulation Language (DML)?

DML enable users to access or manipulate data (retrieval, insertion, deletion). The part of DML that involves information retrieval is called a query language (QL) (structured Query Language- SQL)

 

 

 

Explanation about SQL:

To select those tuples (rows) of the AccCust relation where customer name is “John” it could be written as:

                    6_name =  “John” ^(AccCust)

The results may be one or more records

Comparisons can done using =, >, <, >=,etc.

 

List 4 Field types?

 

1.     INTEGERS e.g. number of population, age

2.     REAL (DECIMAL) e.g. income, salary

3.     CHARACTER  e.g. names, description

4.     DATES    e.g. date of flood