Dimu' Rumpak © 2009 by Prentice Hall 1 Getting Started Didimus Rumpak, M.Si. Database Concepts Chapter 1 1.

1Dimu' Rumpak © 2009 by Prentice Hall

Getting Started

Did

imus

Ru

mpak,

M

.Si.Database Concepts Chapter 1

1

© 2009 by Prentice Hall 2Dimu' Rumpak

Chapter Objectives• Identify the purpose and scope of this

book• Survey the why, what, and how of

database processing• Understand the reasons for using a

database (why)• Learn the functions and components of

database systems (what)• Know the three major steps in creating

a database (how)


Purpose of a Database

• The purpose of a database is to keep track of things

• Unlike a spreadsheet, a database may store information that is more complicated than a simple list


Information Complexity: Redundancy• In a list, each row is intended to

stand on its own. As a result, the same information may be entered several times– For Example: A list of Projects may

include the Project Manager’s Name, ID, and Phone Extension. If a particular person is managing 10 projects, his/her information would have to be entered 10 times


Redundancy Issues

• Redundancy increases input efforts• Redundancy increases

maintenance efforts• Redundancy wastes space and

slows down processing• Redundancy of information may

introduce inconsistencies to the data


Information Complexity: Consistency• In a list, each row stands own its

own. This makes it difficult to apply consistent business rules

• Consider a company that provides discounts for certain customers. To find the appropriate discount would require a search of previous customer orders. This takes time and is prone to error


Information Complexity: Partial Data

• To record information in a list, the record must already exist. This makes it impossible to establish a business rule before a business transaction has occurred

• For example: An order must be entered before a customer’s discount rate may be saved


Information Complexity: Relationships Among the Data• In a list, it is difficult to store information

about more than one topic• For example: A Project List may have

information about the Project, the Project Manager, and the Customer

• As you can image, this list would require many columns. However, the relationships among the Project, Customer, and Project Manager are important


Addressing the Information Complexities

• Relational databases are designed to address many of the information complexity issues


Relational Databases• A relational database stores information

in tables. Each informational topic is stored in its own table

• In essence, a relational database will break-up a list into several parts. One part for each topic in the list

• A Project List would be divided into a CUSTOMER Table, a PROJECT Table, and a PROJECT_MANAGER Table


Microsoft Access: A Database Management System (DBMS)

• To create a relational database, you must use a Database Management System (DBMS) such as Microsoft Access


Putting the Pieces Back Together• In our relational database we broke

apart our list into several tables. Somehow the tables must be joined back together

• In a relational database, tables are joined together using the value of the data

• If a PROJECT has a CUSTOMER, the Customer_ID is stored as a column in the PROJECT table. The value stored in this column can be used to retrieve specific customer information from the CUSTOMER table


Sounds like More Work, Not Less• A relational database is more

complicated than a list• However, a relational database

minimizes data redundancy, preserves complex relationships among topics, and allows for partial data

• Furthermore, a relational database provides a solid foundation for user forms and reports


The User Forms versus Tables

• Although data is stored in several tables, the user forms will look like lists

• This makes it easier for the user to understand. However, in the background the data will be stored in several tables


A Closer Look at a Database System

• The four basic elements of a database are:– Users– Database Applications– Database Management System

(DBMS)– Database


Users

• A user of a database system will provide– Inputs– Modifications– Deletions


Database Applications• A database application is a set of one or

more computer programs that serves as an intermediary between the user and a DBMS

• A database application reads, writes, formats, and/or modifies data. Applications produce:– Forms– Queries– Reports


Functions of a Database Application

• Create and process forms• Create and transmit queries• Create and process reports• Execute application logic• Provide control


Structured Query Language (SQL)

• Structured Query Language (SQL) reads and writes requests for the DBMS

• Many database applications use SQL to retrieve, format, report,

insert, delete, and/or modify data for users


Database Management System (DBMS)

• A database management system (DBMS) serves as an intermediary between database applications and the database

• The DBMS manages and controls database activities


Functions of a DBMS• Create database• Create tables• Create supporting structures• Read database data• Update database data• Maintain database structures• Enforce rules• Control concurrency• Provide security• Perform backup and recovery


Commercial DBMS Products

• Microsoft Access• Oracle’s Oracle• Microsoft’s SQL Server• IBM’s DB2• Dbase IV• Paradox• Foxpro• MySQL


Referential Integrity Constraints• The DBMS will enforce many

constraints. One particularly important constraint is referential integrity

• Referential integrity ensures that the value of a column in one table is valid based on the values in another table– If a 5 was entered as a CustomerID in the

PROJECT table, a Customer having a CustomerID value of 5 must exist in the CUSTOMER table


The Database• A database is a self-describing

collection of related records• Self-describing

– The definition of the structure of the database is contained within the database itself

– Data describing the structure of data is called metadata

• As we’ve seen, tables within a relational database are related to each other


Desktop Database Systems

• Desktop database systems typically:– Have one application– Have only a few tables– Less than ten thousand records– Are simple in design– Involve only one computer– Support one user at a time


Organizational Database Systems• Organizational database systems

typically:– Support several users simultaneously– Include more than one application– Involve multiple computers– Are complex in design– Have large data sets (more than 10,000

records)– Have many tables– Have many databases


Building a Data Model

• Requirements• Design• Implementation


Data Model Requirements and Design• Requirements

– Determine application(s) requirements

– Build data model• Design

– Tables– Relationships– Indexes– Other structures


Data Model Implementation

• Implementation– Create database– Create tables and relationships– Create other structures– Populate with data– Build applications and test


Depicting the Data Model: Entity-Relationship (E-R) Diagram

PROJECTProjIDProjDescStartDate

CUSTOMERCustIDCustName

N:1 0 |


Data Structure Diagram

ProjID | ProjDesc | StartDate | CustID

CustID | CustName 0<

|


Getting Started

Did

imus

Ru

mpak,

M

.Si.Database Concepts Chapter 1

1

Dimu' Rumpak © 2009 by Prentice Hall 1 Getting Started Didimus Rumpak, M.Si. Database Concepts Chapter 1 1.

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