relational databases in enterprise information systems

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IS605/606: Information Systems

Instructor: Dr. Boris Jukic

Relational Database Systems in

Enterprise Information Systems

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File systems

File systems rely on coded file management programs to access,insert and modify their content

As such, file systems are plagued by two main problems

Structural dependence refers to the fact that if a file structure ischanged (such as deletion or addition of a field), the related filemanagement programs have to be modified accordingly

Data dependence refers to the fact that the changes in datacharacteristics, such as changing a field from integer to decimal(or even just changing the length of the field), will cause the

related file management programs to be changed Finally, there is a problem of data redundancy

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Data Redundancy 

When the same data is stored in more thanone location (in multiple files or multiple fields

within one file) It may lead to: Data integrity (inconsistency) problems

may be caused by either data entry errors or failure toupdate all multiple copies of the same data

Data anomalies: modification, insertion anddeletion

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Database Systems

Database Systems achieve data independence andstructural independence If data type of as filed is changed or a field is eliminated or 

a new one added, the existing management programs(queries) do NOT have to be modified

If properly designed, databases have a low level of redundancy, eliminating most of the insertion,deletion and modification anomalies

Logically related data instead of physicallyseparated and unrelated files

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Four (Logical) Data Models

Hierarchical Model (Legacy)

Standard tree-like structure

Network Model (Legacy)

More than one parent allowed Relational Model

First truly data and structurally independent model

No predetermined navigational maps as in two older 

models

The Database technology of choice

Object Model

Tables become objects

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RELATIONAL DATABASE

ADVANTAGES Database advantages from a business

perspective include

Increased flexibility

Increased scalability and performance

Reduced information redundancy

Increased information integrity (quality)

Increased information security

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Relational Database Management System

In RMDBS, all data appears to be stored in acollection of tables (or relations), which are

independent of one another, but can belinked through common entries in one of thetables' columns or fields (controlledredundancy)

Relational Schema: The graph depictingrelationship types between tables

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Relational Schema

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Reduced Data Redundancy 

Products Product Id Product Name Product Description Product Price

001 PlainSounder AM FM Radio, 2 speakers $51.00

002 BetterBox Radio, CD, 6 Speakers $123.00

003 UltraX CD, MP3, 8 Speakers $270.00

Customers

Customer 

ID

Customer 

Name

Customer 

Location

Product

ID

C1 Chrysler Germany 001

C2 Circuit City California 001

H1 Hyundai Korea 001

G1 GM Michigan 002

F1 Ford Motors Michigan 002

H2 Honda Japan 003

B1 BMW Germany 003

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Tables in RDBMS

Tables: Logical constructs containing individual entity sets.  Tables are always two-dimensional: rows and columns

each row represents a single entity (or entity instance) fromthe entity set

each (uniquely named) column represents one attribute each row-column intersection results in a single data value

Each table must have a primary key : An attribute uniquelyidentifying each row (entity), satisfying the entity integrity

conditions. Null value (no entry) is not permitted for aprimary key.

The order of rows and columns within the table is irrelevant 

Foreign Key is an attribute in one table whose values musteither match the value of a primary key in another table or be set to null (no value). These conditions are known as

referential integrity constraint.

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Relationships within the relational

database:� One-to-one relationships:

� One-to many relationships:� Examples:

� professor - class� department - employee

� Many to-many relationships� Examples: parts ± product, student ± class, «

� it is recommended to break it into a set(usually two) of one-to-may relationshipsthrough a so called composite (bridge) entity

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Enterprise data planning 

� A large component of the business

informational needs can be captured bythe mapping of all entities theorganizations need to keep track of andthe relationships among them

� E-R (Entity-Relationship) modeling is astandard technique that provides a simplifiedpicture of the relationship among entities.

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K eys and Relationships: transaction

processing system example

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RELATIONAL DATABASE

ADVANTAGES Database advantages from a business

perspective include

Increased flexibility

Increased scalability and performance

Reduced information redundancy

Increased information integrity (quality)

Increased information security

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Increased Flexibility 

A well-designed database should:

Handle changes quickly and easily

Provide users with different views

A database has only one physical view

Physical view ± deals with the physical storage of information on a storage device such as a hard disk

A database can have multiple logical views

Log ical view ± focuses on how users logically accessinformation to meet particular business needs

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Increased Scalability and Performance

A database must scale to meet increaseddemand, while maintaining acceptableperformance levels

S calability ± refers to how well a system canadapt to increased demands

Perf ormance ± measures how quickly a systemperforms a certain process or transaction

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Reduced Information Redundancy 

Databases reduce information redundancy

R edundancy ± the duplication of information or storing the same information in multiple places

Inconsistency is one of the primary problemswith redundant information

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Increase Information Integrity 

(Quality) I nf ormati on integ rity ± a measure of the quality of information

I nteg rity c onstraints ± rules that help ensure the quality of information

Operati onal integ rity c onstraints ± rules that enforcebasic and fundamental information-based constraints

Business-critical integ rity c onstraints ± rules thatenforce business rules vital to an organization¶s successand often require more insight and knowledge than

operational integrity constraints

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Increased Information Security 

Information is an organizational asset andmust be protected

Databases offer several security featuresincluding:

Passwords ± provide authentication of the user 

Access levels ± determine who has access to thedifferent types of information

Access controls ± Determine types of user access, such as read-only access

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DATABASE MANAGEMENT

SYSTEMS Database manag ement systems ( DBM S) ±

software through which users and applicationprograms interact with a database

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INTEGRATING INFORMATION

AMONG MULTIPLE DATABASES Organizations typically maintain multiple

systems, each with its own database

I nteg rati on ± allows separate systems tocommunicate directly with each other 

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INTEGRATING INFORMATION

AMONG MULTIPLE DATABASES F orward integ rati on ± takes information entered into a given systemand sends it automatically to all downstream systems and processes

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INTEGRATING INFORMATION

AMONG MULTIPLE DATABASES Backward integ rati on ± takes information entered into a given systemand sends it automatically to all upstream systems and processes

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INTEGRATING INFORMATION

AMONG MULTIPLE DATABASES

Building acentral

repositoryspecificallyfor integratedinformation