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DATABASE
TECHNOLOGIES
(Week 3, Tuesday 9/4/2007)
BUS3500 - Abdou Illia, Fall 2007
1
LEARNING GOALS

Explain basic concepts of data management.

Describe file systems and identify their
problems.

Define database management systems and
describe their various functions.

Explain how the relational database model
works.

Describe how databases are developed.
2
Basic Concepts of Data Management
Table 1
Table 2
Form 1
Acc #:_______
Name:_______
Table 3
Report
Database:
Collection of data
organized in
different
containers
3
Basic Concepts of Data Management
Accounts table



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

AccountID Customer
Type
Balance
660001
John Smith
Checking
$120.00
660002
Linda Martin
Saving
$9450.00
660003
Paul Graham
Checking
$3400.00
Each table has:



Fields
Records
1 Primary key
Table

Two-dimensional structure composed of rows and columns

Like a column in a spreadsheet


Like a column name in a spreadsheet
Examples: AccountID, Customer, Type, Balance

Actual data for the field

Set of fields that describe an entity (a person, an account, etc.)

A field, or group of fields, that uniquely identifies a record
Field
Field name
Field values
Record
Primary key
4
Basic Concepts in Data Management

A Primary key could be a single field like in this table

A Primary key could be a composite key, i.e. multiple fields
5
Traditional File Systems

System of files that store groups of records
used by a particular software application

Simple but with a cost




Inability to share data
Inadequate security
Difficulties in maintenance and expansion
Allows data duplication (e.g. redundancy)
Application 1
Application 2
Program 1
Program 2
Program 1
Program 2
File 1
File 1
File 1
File 1
File 2
File 2
File 2
File 2
File 3
File 3
File 3
File 3
6
File System Anomalies

Insertion anomaly


Modification anomaly



Data needs to be entered more than once if
located in multiple file systems
Redundant data in separate file systems
Inconsistent data in your system
Deletion anomaly


Failure to simultaneously delete all copies of
redundant data
Deletion of critical data
7
Database Management System (DBMS)

Combination of software and data for


Collecting, storing and managing data in a
database environment.
A DBMS includes:



Database
Database engine (for accessing and modifying
the DB content)
Data Manipulation Language
Application 1
Program-1
Application 2
Program-2
Program-1
DBMS
Program-2
8
DBMS Functions
Store data (in tables) on secondary storage
 Transform data into information (reports, ..)
 Provide user with different logical views of
actual database content
 Provide security


DBMSs control who can add, view, change, or
delete data in the database
Physical view
ID Name Amt
01 John 23.00
02 Linda 3.00
03 Paul 53.00
ID
02
Name
Paul
Logical views
Name
Linda
ID Name Amt
01 John 23.00
02 Linda 3.00
Amt
53.00
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More DBMS Functions

Allow multi-user access

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Control concurrency of access to data
Prevent one user from accessing data that has
not been completely updated

When selling tickets online, Ticketmaster allows you
to hold a ticket for only 2 minutes to make your
purchase decision, then the ticket is released to sell
to someone else – that is concurrency control
10
Types of DBMSs

Desktop

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Used by individuals or small groups
Requires little or no formal training
Does not have all the capabilities of larger
DBMSs
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Types of DBMSs (Continued)

Enterprise


Serve multiple locations and store large amounts of data
Either centralized or distributed

Centralized – all data on one server
 Easy to maintain
 Prone to run slowly when many simultaneous users
 No access if the one server goes down

Distributed – each location has part of the database
 Very complex database administration
 Usually faster than centralized
 If one server crashes, others can still continue to operate.
12
Database Models

Database model = a representation of the
relationship between structures (e.g.
tables) in a database

Four common database models

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Flat file model
Hierarchical, or tree structure, model
Network model
Relational model (this one is the most
common)
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Flat File Database
Stores data in basic table structures
 No relationship between tables
 Used on PDAs for address book

14
Hierarchical Database Model
Resembles an inverted tree, with the root
at the top
 Limited to storing data in one-to-many
relationships


One parent segment to many child segments
Very fast when searching large amounts
of data in a pre-specified order
 Not very flexible

15
Network Model

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Many-to-many relationships between tables
Any record may be linked to any other record
Highly flexible but also highly complex
Rarely used
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Relational Model

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Multiple tables related by common fields
Uses controlled redundancy to create fields that
provide linkage relationships between tables in the
database
 These fields are called foreign keys – the secret to
a relational database
 A foreign key is a field, or group of fields, in one
table that is the primary key of another table
Somewhat slower than hierarchical and network DBMSs
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Database Development
Analyze data needs and use
Develop conceptual model
Develop physical model
Implement database
Administer database
1) Analysis
•
•
Develop a clear understanding of how the
organization works and what data is used
Determine data needs of each functional
area
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Database Development Process
(Continued)
2) Develop a conceptual model –
•
•
•
Show how data are grouped together and
related to each other
Entity-Relationship diagrams (ERDs) are
used
Less expensive to correct an ERD than to
redesign an already constructed database
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Database Development Process
(Continued)
3) Develop a physical model –
•
•
•
Physical model provides specific details about
each table and field in the database
Normalization used to remove redundant
data and therefore minimize any anomalies
Optimize the database for performance
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Database Development Process
(Continued)
4) Database implementation
•
•
•
Install the DBMS software
Build the database
Test
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Database Development Process
(Continued)
5) Database administration
•
•
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Ensures database efficiency
Manages backup and restoration
Sets up user accounts and security
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Summary Questions
Notes
1) What is a table, a field, a record, a primary key, a composite
key?
4-5
2) What are the problems with traditional file systems?
6,7
3) What are the major components of a DBMS?
8
4) (a) Name some Desktop DBMSs. (b) Name some Enterprise
DBMSs.
5) What are the differences between Flat File and Relational
database models?
6) What are the steps for Database development?
14,17
18-
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