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Basic database terminology and concept
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DATA REPRESENTATIONDATA REPRESENTATION
Analog vs. Digital Digital
Two states (1) on (0) off
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DATA REPRESENTATIONDATA REPRESENTATION
Binary number system Combination of ones and zeroes
represent characters
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Bit and Byte
Bit Short for binary digit Smallest element of data Either zero or one
Byte Group of eight bits, which operate as a
single unit Represents one character or number
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Representing Characters in Bytes
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Using Binary Code to Calculate
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Hierarchy of Data
Bit Byte (Character) Field Record File Database
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Database objects/tools
Table Form Query Report
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Table
A table is a grid of rows and columns
R O WCOLUMN
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Field
A single trait or characteristic about a subject of a table
NAMA TARIKH LAHIR
JANTINA NO TEL GAJI
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Data type
Characteristic designate for an Access field Text Number Currency Date/time Yes/No Memo OLE object Hyperlink
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Exercise
Salutation (Mr., Mrs., Ms.) Date of birth Home address Whether a student is allergy to
medication The words to describe type of allergy Photo of a student How many sibling in the house Salary
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Record
A group of traits about a particular item Simply a row in a table!
NAMA TARIKH LAHIR
JANTINA NO TEL GAJI
…
…
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Value
The actual data entered at the intersection of a row and column
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Primary keys
Key is a field that serves a specific function within a table.
AutoNumber Requirement for a relational database.
Means, in a field that is the primary key, there can never be duplicate data
example
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It’s about nothing: Null values and Zero-Length strings
“Report that say something hasn’t happen are always interesting to me because, as we know, there are known knowns, there are things we know we know. We also know there are known unknowns; that is to say, we know there are some things we do not know. But there are also unknown unknowns-the ones we don’t know we don’t know”
At a press conference in 2003Donald Rumsfeld
Secretary of Defense(in the Bush Administration)
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It’s about nothing: Null values and Zero-Length strings
Example:
Student Name Has Tel. No.? Tel. No.
Jasman Yes 018-1234567
Asmah No Does not exist
Syafiq Yes Exist, but we don’t know it
Elangovan Don’t know Don’t know if there’s one
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Activity 2
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Creating a Database
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Three main steps
Determine the data you need You describe the data You enter the data into the database
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Determine Data Needs
Two basic approaches can be used to determine data needs: A process-oriented approach An enterprise modeling approach
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A process-oriented approach
To define data needs in a process-oriented approach:
1. Define the problem
2. Identify necessary decisions
3. Describe information needs
4. Determine the necessary processing
5. Specify data needs
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A process-oriented approach
Sometimes called the problem-oriented approach
Because it begins with a problem A problem can be good or bad
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A process-oriented approach
Once problems are identified, the data and processes dealing with problem solutions can be determined
The strength is that it addresses problems well
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A process-oriented approach
Although the process-oriented approach enables the data needs of each system to be defined in a logical manner, its weakness is the difficulty of linking the data from one problem to another
IS cannot easily share data if they are isolated from other IS dealing with other kind of problems.
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Enterprise modeling approach
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Data Planning Process
Database development is a top-down process Develop an enterprise model that defines the
basic business process of the enterprise
Define the information needs of end users in a business process
Identify the key data elements that are needed to perform specific business activities (entity relationship diagrams)
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Enterprise modeling approach
The strength of this approach is that it takes advantages of a broad view of data resources
All areas are considered, and synergy of data resources between areas can be leveraged
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Enterprise modeling approachStrategic Planning for information resources
Create an enterprise data
model Determining all of the org.’s data needs
Create database
Storing that datain the database
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Data Modeling Techniques
Modeling the org.’s data needs is supported by techniques that describe the data, how the data aggregates into tables, and how tables relate to each other.
A number of techniques: entity-relationship diagrams and class diagrams
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Entity-relationship diagrams
Are used to describe relationships between conceptual collections of data so that their related records can be joined together
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Class diagrams
Are used to describe both the data relationship and the actions that operate on the data in the relationships
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Entity-relationship diagrams
ERDs Deal with data in entities and the
relationships between entities Entities – conceptual collections of
related data fields Tables are the result of breaking
entities into smaller units that conform to the rules for database structures
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Entity-relationship diagrams
An entity may turn into table, but frequently an entity is broken into several tables
ERDs are a higher level conceptualization of data than tables
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Entity-relationship diagrams
Entities in ERDs will have names and relationship links
ERD relationships will denote if a record in one entity will relate to one or more records in other entity
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Entity-relationship diagrams
Let us assume that we need to describe the data needed for a new IS: IS Sekolah SAYA
3 separate data entities will exist: … … …
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1 1
M M
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To read the relationship:
One-to-many relationship - “one school record may relate to many staff records and one staff record may relate to only one school record”
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M
M
Many-to-many relationship
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Many-to-many relationship
A single subject could have many staff, and a single staff could be on many subject
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M
M
1
M
1
M
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Class Diagrams
clsStaf
Name
Salary
HireDate
addStaf
deleteStaf
updateStaf
clsMataPel
Title
Ting
addMataPel
deleteMataPel
updateMataPel
1…*
1…*
clsSchool
SchoolName
Adress
addSchool
deleteSchool
updateSchool
clsStud
Name
IC
StudAdd
addStud
deleteStud
updateStud
ExamStud
1…*
1…*1
1
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Using the database
Forms, reports and queries are common methods for accessing the database held in database management system
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Database Structures
In all IS, data resources must be organized and structured in some logical manner so that they can be accessed easily, processed efficiently, retrieved quickly, and managed effectively.
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Database Structures
Common database structures… Hierarchical
Network
Relational
Object-oriented
Multi-dimensional
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Hierarchical Structure
Early DBMS structure Records arranged in tree-like structure Relationships are one-to-many
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Network Structure
Used in some mainframe DBMS packages Many-to-many relationships
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Relational Structure
Most widely used structure Data elements are stored in tables Row represents a record; column is a field Can relate data in one file with data in another,
if both files share a common data element
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Relational Operations
Select Create a subset of records that meet a stated
criterion Example: employees earning more than $30,000
Join Combine two or more tables temporarily Looks like one big table
Project Create a subset of columns in a table
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Multidimensional Structure
Variation of relational model Uses multidimensional structures to
organize data
Data elements are viewed as being in cubes
Popular for analytical databases that support Online Analytical Processing (OLAP)
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Multidimensional Model
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Object-Oriented Structure
An object consists of Data values describing the attributes of an entity Operations that can be performed on the data
Encapsulation Combine data and operations
Inheritance New objects can be created by replicating some
or all of the characteristics of parent objects
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Object-Oriented Structure
Source: Adapted from Ivar Jacobsen, Maria Ericsson, and Ageneta Jacobsen, The Object Advantage: Business Process Reengineering with Object Technology (New York: ACM Press, 1995), p. 65. Copyright @ 1995, Association for Computing Machinery. By permission.
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Object-Oriented Structure
Used in object-oriented database management systems (OODBMS)
Supports complex data types more efficiently than relational databases Examples: graphic images, video clips,
web pages Example use for product design
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Evaluation of Database Structures Hierarchical
Works for structured, routine transactions Can’t handle many-to-many relationship
Network More flexible than hierarchical Unable to handle ad hoc requests
Relational Easily responds to ad hoc requests Easier to work with and maintain Not as efficient/quick as hierarchical or network
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Database Development
Database Administrator (DBA) In charge of enterprise database development
Improves the integrity and security of organizational databases
Uses Data Definition Language (DDL) to develop and specify data contents, relationships, and structure
Stores these specifications in a data dictionary or a metadata repository
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Data Dictionary A data dictionary
Contains data about data (metadata) Relies on specialized software component to
manage a database of data definitions
It contains information on.. The names and descriptions of all types of data
records and their interrelationships Requirements for end users’ access and use of
application programs Database maintenance Security
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Based on database structure above, describe the characteristics of the IS or the organization which hold the IS. Use the following table for discussion:
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System typesSimple Complex
Has few components, and the relationship or interaction between elements is uncomplicated and straightforward
Has many elements that are highly related and interconnected
Open Closed
Interact with its environment Has no interaction with the environment
Stable Dynamic
Undergoes very little change over time Undergoes rapid and constant change over time
Adaptive Non-adaptive
Is able to change in response to changes in the environment
Is not able to change in response to changes in the environment
Permanent Temporary
Exists for a relatively long period of time Exists for only relatively short period of time
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Database Structures
Source: Management Information Systems by James A. O'Brien and George Marakas. McGraw-Hill Higher Education
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