Transcript Supply Chain Enterprise Resources Planning and Business

Technology Guide 3
Data and Database
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IT for Management
Prof. Efraim Turban
File Management
Database
File
File
Record
Field
Byte
Field
Field
Byte
Bit
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Record
Field
Byte
Bit
Bit
Byte
Bit
Hierarchy of data for a computer-based file
IT for Management
Prof. Efraim Turban
File Management
• Entity
– a person, place, thing, or event on which
we maintain information
• Attribute
– characteristic or quality describing a
particular entity
– corresponds to a field
• Key Field
– a file that uniquely identifies that record
– an identified filed
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IT for Management
Prof. Efraim Turban
Accessing Records from
Computer Files
• Sequential File Organization
– data records must be retrieved in the
same physical sequence in which they
are stored
– magnetic tape
• Direct or Random File Organization
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– Users can access records in an
sequence, without regard to actual
physical order on the storage medium
– magnetic disks
IT for Management
Prof. Efraim Turban
Problems Arising
from the Environment
• Data Redundancy : the same piece of information could be
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•
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•
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duplicated in several files
Data Inconsistency : the actual values across various
copies of the data no longer agree
Data Isolation : data files are organized differently, stored
in different formats, and often physically inaccessible to
other applications
Security : new application may be added to the system on
an ad hoc basis
Data Integrity : data values must often meet integrity
constraints
Application/Data Independence : application should not
have to be developed with regard to how the data are stored
IT for Management
Prof. Efraim Turban
Database and
Database Management Systems
• Database
– an organized logical grouping of related files
– no data redundancy, data isolation, and data
inconsistency
• Database Management Systems (DBMS)
– a program that provides access to a database
– permits an organization to centralize data,
manage them efficiently, and provide access
to the stored data by application programs
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Prof. Efraim Turban
Specialized Database
• Geographical Information Database
– contains locational data for overlaying on
maps or images
• Knowledge Database
– stores decision rules used to evaluate
situations and helps users make decisions
like an expert
• Multimedia Database
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– Stores data on many media – sounds,
video, images, graphic animation, and text
IT for Management
Prof. Efraim Turban
Data Definition Language
(DDL)
• Schema
– the logical description of the entire
database and the listing of all the
data items and the relationships
among them
• Subschema
– the specific set of data from the
database that is required by each
application
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Prof. Efraim Turban
Data Manipulation language
(DML)
• Structured Query Language (SQL)
– combines both DML and DDL features
– offers the ability to perform complicated
searches with relatively simple statements
• Query-by-example (QBE)
– allows users to select a table and chooses
the fields to be included in the answer as
the example he provided
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Prof. Efraim Turban
Data Dictionary
• Data dictionary is a file that stores
definitions of data elements and
data characteristics such as usage,
physical representation, ownership,
authorization, and security
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Prof. Efraim Turban
Hierarchical Database Model
• It relates data by rigidly structuring data
into an inverted “tree”
• A single root or master field (Key)
– identifies the type location, or ordering of
the records
• A variable number of subordinate fields
– defines the rest of the data within a record
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Prof. Efraim Turban
Network Database Model
• It creates relationships among data
through a linked-list structure in
which subordinated records can be
linked to more than one parent
• Pointers
– link subordinates and parents
– storage addresses that contain the
location of the related record
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Prof. Efraim Turban
Relational Database Model
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• It is based on the simple concept of
tables in order to capitalize on
characteristics of rows and columns
of data, which is consistent with
real-world business situations
• Relations : table
• Record : row of data
• Field : column of data
• Object-relational Database Systems
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Prof. Efraim Turban
Creating Database
• Conceptual Design
– an abstract model of the database
from the user or business perspective
– Describes how the data elements in
the database are to be grouped
• Physical Design
– shows how the database is actually
arranges on direct access storage
devices
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Prof. Efraim Turban
Entity-relationship Modeling
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• Entity is something that can be identified
in the users’ work environment
• Instance of an entity is the representation
of a particular entity
• Attributes describe the entity’s
characteristics
• Identifiers are attributes that identify
entity instances
• Relationships can include many entities
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Prof. Efraim Turban
Entity-Relationship Diagram
Name
Departmet
Attribute
Entity
Major
Student
ID Number
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Relationship
Table
Class
1:N
One to many
Name
Professor
Class Taught
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Prof. Efraim Turban
Normalization of
Relational Databases
• Functional Dependency
– a relationship between or
among attributes, where,
given the value of one
attribute, we can obtain the
value of another attribute
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Prof. Efraim Turban
Emerging Database Models
• Multimedia Database : an additional
database that enables end users to quickly
retrieve and present completes data that
involve many dimensions
• Deductive Databases
• Object-oriented Database : used for OO
programming
• Multimedia and Hypermedia Database
: analogous to textual and numeric data
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Prof. Efraim Turban
Data Warehouses
• It is an additional database that is designed to
support DSS, EIS, online analytical process
(OLAP), and other end-user activities.
• It can provide an “executive view” of data
and a unified corporate picture to the endusers by combining the data from many
operational systems and incompatible
databases without affecting the performance
of the running operational systems
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Prof. Efraim Turban
Database Topology
• Centralized Database has all the related
files in one physical location
• Distributed Database has complete
copies of a database, or portions of a
database, in more than one locations
• Replicated Database has complete copies
of the entire database in several locations
• Partitioned Database is subdivided, so
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that each location has a portion of the entire
database
IT for Management
Prof. Efraim Turban
Physical vs. Logical Data View
• Physical View
– deals with the actual, physical
arrangement and location of data in the
direct access storage devices (DASD)
• Logical View
– represents data in a format that is
meaningful to a user and to the software
programs that process that data
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IT for Management
Prof. Efraim Turban
Database Management
• Database Design
• Database Implementation
• Database Administrators
– responsible for ensuring that the
database fulfills that user’s business
needs, in terms of functionality s
well for the data itself
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Prof. Efraim Turban
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