DATABASE CONCEPT

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DATABASE CONCEPT

• Database can be defined as a collection
• of information organized in such a way that
• it can be accessed easily.
• Examples of database
• Telephone directory
• Tracking customer orders
• Maintain employees records.

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Database Terminologies

• Data
• This is the fact, or about specific
  entity(person,place or thing)
• Information
• Is the data that have been processed and is
  useful to the user
• Field
• Is a single item of information or data in entity
• e.g. employee name
• Record
• Is a group of fields about an entity,example
• Employees particulars

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History of databases

• Manual system
• Before the advent of the ideas behind the modern
  database systems,
• it was common for different firm to store
  information using manual system.
• Structure of manual system
• Information concern all division in the firm, can
  be stored in dedicated room or each division
  such as sales, accounts, production can be stored
  in there own information separate offices
• Room or office will be furnished with
  shelves,that holds records for different subjects
• Information will be stored in hard flat files,
  each file will carry one record
• Each file will have a specific number to identify
  it
• A person will use a file number to retrieve it

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MANUAL FILE SYSTEM

• USER

FILE KEEPER
FILE CABINET
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• If management wanted an overall view of the
  firm,they would have to gather lots of
  information from many different divisions before
  the appropriate statistic could be obtained .
• This process was too laborious to be considered
  and thus vital information in decision making
  could be lost
• Due to this problem the modern database
  ideas(FPS) were born

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FILE PROCESSING SYSTEM

• Information stored as group of records in
  separate files
• File systems consisted of a few data files and
  many application programs
• Each file called a soft file
• Flat file contained the processed information for
  one specific function
• Use of programming languages to write
  applications

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File processing systems structure
Customer Processing Application
Customer file
Customer file
User 1
Rental file
Rental Processing Application
Rental file
User 2
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Limitation of File Processing system

• Separate and isolated data
• To make decision, user might need data
  from more
• than one file
• Data redundancy
• often the same information was stored in
  more than one file, in addition to taking up
  more space in the system, this cause loss of data
  integrity
• Program
• data independence for file formats and
  access techniques

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• Difficult in representing data from users view
• To create useful application for user,
  often data from various files must be combined.
  In file processing system, it was difficult to
  determine the relationship between isolated data
  in order to meet user requirement.
• Data inflexibility
• Program-data independency and data
  isolation limited the flexibility of the file
  processing system in providing user requirement
• Due to this limitations, the concept of
• Data base management system (DBMS) was born

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DATA BASE MANAGEMENT SYSTEM(DBMS)

• Is a program that allows users to define, create,
  manipulate, store, maintain retrieve and process
  the data in the data base in order to produce
  meaningful information.
• Focus on information presentation
• Data stored as a records in various database
  files that can be combined to produce meaningful
  information for users
• It controls all functions of capturing,
  processing, storing, retrieving data and
  generates various forms of data output
• Manage access by multiple users and multiple
  programs to common stored data.
• And hence it overcomes all limitations of FPS

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DBMS STRUCTURE
USER 1
CPA
DATABASE
DBMS
RPA
USER 2
OPA
USER 3
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• CHARACTERISTICS OF DMS
• Computerized record keeping system
• Contain facilities that allow user to
• (a)add, and delete files
• (b)Insert,retrieve, update, delete data
• Collection of databases each can be used for
  separate purposes or combined

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EXAMPLES OF DBMS

• Ms ACCESS
• SQL SERVER
• ORACLE
• MY SQL

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FUNCTIONS OF DBMS

• To store data
• To organize data
• To control access to data
• To protect data

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USES OF DBMS

• To provide decision support
• To provide transaction processing

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COMPONENTS OF DBMS

• The basic components of a DBMS can be divided
  into three subsystem
• Design tool
• This provide features for creating the data
  base and various application, forms, and reports
• Run-time facilities
• This process the application created by
• design tools.
• DBMS engine
• Translates between the design tools and
  run time facilities and data

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ADVANTAGES OF DBMS

1. Centralized data reduce management problems
2. Data redundancy and consistency are controllable
3. Program-data interdependence is diminished
4. Flexibility of data is increased

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DISADVANTAGES OF DBMS

1. Reduction in speed of data access time
2. Require special knowledge
3. Possible dependency of application programs to
   specific DBMS versions

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DATABASE ADMINISTRTATOR

• Is a one who controls and manage the data base
• Functions of DBMS
• To make decisions concerns the content of the
  data base
• Plan storage strictures and access strategies.
• Provide user support
• To define security and integrity checks
• Interpret backup and recovery strategies

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TYPES OF DATABASES

• There are four common types of database models,
• which are
• Flat
• Hierarchical
• Network
• Relational

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FLAT DATABASE MODEL

• The earliest and simplest database model
• Is a way of organizing information in a single
  table
• Is good only for simple database
• Possible redundancy of data

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HIERARCHICAL DATABASE MODEL

• As its name implies, the hierarchical database
  model defines hierarchically arrangement of data
• Is like upside down tree
• A single table acts as a root of the database
  from which the other table branches out
• Relationship in such system are thought of in
  terms of children an parents, such as a children
  may have only one parent but a parent can have
  multiple children

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• Parents and children are tied together by links
  called pointers
• More efficient than Flat database
• Has some serious problems, that you can not add a
  record to a child table until it has already been
  incorporated with the parent
• Redundancy of data may occur because it does not
  handle many to may relationship

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NETWORK DATABASE MODEL

• It was designed to solve problems of hierarchical
  data base model
• It solves the problem of data redundancy by
  representing relationship in terms of sets rather
  than hierarchy
• It is similar to the hierarchical model, in fact
  the hierarchy model is a subset of network model
• But this model was difficult to implement, so
  another simple model was developed, which is
  RELATIONAL DATABASE MODEL

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RELATIONAL DATABASE MODEL

• Is a collection of data items organized as a set
  of formally-describes tables from which data can
  be accessed or reassembled in many different ways
  without having to reorganize the data base tables
• A collection of data organized in
  two-dimensional tables consisting of named
  columns and rows
• It is easy to create
• It is easy to extend, after original database
  creation.
• The core of Relational data base model is the
  concept of table, which is also called relation
  in which all data is stored

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• Each table is made up of records (horizontal
  rows also known as tuples) and fields (vertical
  column also known as attributes)
• Table-is a two dimensional representation of data
  consisting of column and zero or more rows
• The table name must be unique
• The table name must be descriptive
• Column name must be unique within the table,
  however those columns in different tables my
  share the same name
• Rows must be unique

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• Null values-is a missing or unknown value in a
  column of a table, null are not the same as zeros
• Primary key-is the column or group of columns
  whose values uniquely identify each row of a
  table
• Every table must have only one PK
• Pk must always have a value
• PK must be unique
• Foreign key is a column or group of columns that
  is a primary key in another table, it relates the
  rows of the table to other rows that appear
  elsewhere in another table

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DATABASE DEVELOPMENT

• The process can be broken into 5 phases
• (i)Planning
• (ii)Analysis
• (iii)Design
• (iv)Implementation
• (v)Maintenance
• These phases often overlap, and some techniques
  and tools may be used in more than one stage,
  especially between analysis and design. E.g Data
  Dictionary
• Data base design is non deterministic

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PLANING PHASE

• Here the overall database structure is defined.
• It involves the following tasks
• 1. The purpose of database is
  determined
• What information will be used
• How information is to be use
• What question will be answered
• 2. Feasibility study are conducted
• 3. Requirements are gathered
  

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Analysis phase

• Database can be analyzed on different models
• Conceptual model
• Logical model
• Physical model
• Conceptual model
• It provide the framework for developing a
  database structure schema from top to down
• Three data base components (entities,attributes
  an relationship) are described in detail.
  

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• Entities
• This defines a thing that exist and is
  distinguishable from which data will be
  collected, e.g person,place or object.
• These are are basic building blocks of database
• Entity instance
• Is a particular occurrence of an entity
• Entity set/class/type
• A group of similar entities
• Attributes
• This describes the properties of entities
• and relationship

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• Relationship
• A relationship is a connection between entity
  classes.
• Example, relationship between PERSONS
• and AUTOMOBILES could be an OWNS
• That is to say , people own automobile
• Types of relationship
• We have three types of relationship
• 1.one-to-one
• 2. One-to-may
• 3.Many-to-many
• Candidate keys

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• Logical model
• This is done after conceptual model
• Tables and fields are extracted
• Entities modeled as tables
• Attributes modeled as fields
• Each entity instance is called a record.
• PK and FK are determined
• After that Normalization process takes place
• Physical model
• This defines how data will be stored and accessed
  in a computer system

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DESIGN PHASE

• This determines how best the information system
• that was obtained
• The following should be determined and
• and represented in design phase
• Tables needed
• Fields needed for each table
• Relationships between tables
• DBMS
• User views (Input forms, output reports)
• Security mechanism

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Database Management Systems (DBMS)

• Abdallah Seleman
• Computing and Information Technology Dept.
• The Institute of Finance Management

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Course Co-ordinator

• Abdallah Seleman
• dullextz_at_gmail.com
• Block D,55
• Consultation Hours
• Tuesday Wednesday
• 1000 AM-1200PM

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An Integrated of -

• Introduction
• Fundamentals of database
• File Processing
• Database processing
• Common database software
• Database Management Systems (DBMS)
• Relational Database Management Systems (RDBMS)
• Data Normalization
• Introduction to Structured Query Language (SQL)
• Implementation of a Relational Database using a
  RDBMS

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Recommended Readings

• Leon, A. and Leon,M (2002) Database Management
  Systems,Dar es Salaam University Press
• Narang, Rajesh (2004) Database Management
  Systems, New Delhi
• David Kroenke (2002), Database Processing
  Fundamentals, Design and Implementation, 8th
  Edition, Prentice Hall, Upper Saddle River NJ
• Thomas M. Connolly and Carolyn E. Begg (2002),
  Database Systems A Practical Approach to Design,
  Implementation, and Management, 3rd Edition,
  Addison-Wesley, Harlow England.
• Note, Additional Readings shall be provided if
  necessary.

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Outline

• Fundamentals of Database
• File Processing
• Advantages Disadvantages of File Process
  Approach
• Data Processing
• Data Management
• Data Independence
• Data Administration Roles

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Assessment

• You will be assessed through continuous
  assessments (Coursework) that comprise of two
  compulsory Tests, quizzes and assignments
• You are required to seat for a final examination
  at the end of the semester II

• CourseWork carries 40
• Final Examination carries 60

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Fundamentals of Database

• Computer uses databases by using a set of well
  defined rules.
• Example, Assume that each card in the mailbox has
  five lines of data items, namely as-
• Name, Locality, City, State and Pin_Code
• These fields combined to form a record.
• Generally, A database contains the following.
• Field
• Record
• File
• Database
• Key Field

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Fundamentals of Database.
Figure 1 Illustrates the concepts of Fields, Records, and Files
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Fundamentals of Database.

• Field
• The smallest piece of meaningful information in a
  file is called a data item or Field.
• A data item is generally used for a group of
  alphanumeric characters.
• Example, Name, Locality, City, State, Pin_Code
  are all known as Data Items or Fields as shown in
  figure 1

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Fundamentals of Database.

• Record
• Collection of related fields
• Example, Figure 1 contains four records and each
  record has five related fields namely as
• Name, Locality, City, State and Pin_Code
• File
• Is the Collection of all related records.
• Example, in figure 1, the file contains the list
  of addresses of four friends.

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Fundamentals of Database.
Figure 2 illustrates the concepts of Fields, Records, Files and Database
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Fundamentals of Database.

• Database
• Database is a collection of related files.
• A database is an organised collection of facts
• Is a Collection of information arranged and
  presented to serve an assigned purpose
• Examples-
• A dictionary, where words are arranged
  alphabetically
• Telephone directory where subscriber names are
  listed in alphabetic order.
• Figure 2 shows Employees Database having related
  files containing records of employees

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Fundamentals of Database.

• Key Field
• The Keyfield in a record is a unique data item
  which is used to identify the record for the
  purpose of accessing and manipulating database
• In figure 2,
• File 1 contains employee records with fields
  Emp_Code and Address,
• File 2 contains employee records with fields
  Emp_Code and Salary
• File 3 contains employee records with fields
  Emp_Code and Name
• All the three files have one common field,
  namely Emp_Code, this field is called the
  Keyfield Is used for identifying and relating
  records

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File Processing

• Data, Information, Knowledge

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File Processing.

• Data
• Are raw facts which can be manipulated
• Data is required in the operation of any
  organisation and the same or similar data may be
  required for various purposes
• Information
• The manipulation of data, simply information is
  summarization of data in presentable form
• Data consists of facts which become information
  when they are processed and convey meaning to
  people.
• Information is the backbone of any organisation
• Information is the critical factor that enables
  managers and organisations to gain a competitive
  advantage. It can be considered as the most
  critical resource of an organisation.

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File Processing.

• Information..
• It is the indispensable link that ties together
  all the components of an organisation for better
  operation and coordination and for survival in
  todays brutally competitive environment.

Definition, Information is data that have been put into a meaningful and useful context and communicated to a recipient who uses it to make decision (Burch and Grudnitski,1989)
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File Processing.

• Information.
• It involves the communication and recipient of
  intelligence or knowledge
• It should predict the future with reasonable
  level of accuracy
• It should help the managers make the best
  decision and a prevent them from taking wrong
  decision
• It consists of data , images , text , documents
  and voice often inextricably intertwined but
  always organised in a meaningful context.

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File Processing.

• Information..
• Notice that the data that is being processed or
  refined can be input, stored or both and this
  formulates the cycle of information, refer figure
  3.
• Example, If orders and payments are data, then
  balance_due and quantity_in_hand would be the
  information
• Knowledge
• Refers to as the facts , events and inference
  rules used by a computer program in order to
  operate intelligently.
• It refers to a persons capability and wisdom as
  how much that person knows about one particular
  subject

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File Processing.
Figure 3, Information Cycle
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File Processing.

• Information Processing
• Information processing is the acquisition,
  storage, organisation retrieval, display and
  dissemination of information
• Quality information means that the information
  that is
• Accurate
• Timely
• Relevant

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File Processing.

• Files, File organisation and Management
• File
• A file is a collection of bytes stored as an
  individual entity
• All data on disk is stored as a file with an
  assigned file name that is unique within the
  directory it resides it.
• To the computer, a file is the series of bytes
• The structure of a file is known to the software
  that manipulate it.

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File Processing.

• File..
• It contains data that is needed for information
  processing
• These data is called entities, An entity is
  anything about which information can be stored,
  examples, physical object, a person, concept or
  event and so on
• An attribute is a characteristic of interest
  about an entity.

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File Processing.

• File..
• The values of the attributes describe a
  particular entity.
• An Instance of the entity is represented by a set
  of specific values for each of the attributes

Examples, Entity a car Attributes (car) Make, Model, Price, Eng. Capacity Instances (car) Mercedes-benz, S500, 12,000, 4956cc
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File Processing.

• File..
• In data storage, data items are usually grouped
  together to describe an entity
• There are different types of files,
• Master files
• Transaction files
• Report files

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File Processing.

• Master files
• A file of relatively permanent information about
  entities
• These files are used as a source of reference
  data for processing transactions and accumulated
  information based on the transaction data.
• Example, the accounts master file in a bank will
  contain details like account name, balance,
  address and so on

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File Processing.

• Transaction Files
• A collection of records describing activities or
  transactions by organisation.
• Created as a result of transactions and preparing
  transaction documents
• Are used to update the details in the master file
• Example in the same bank system, the day-to-day
  activities like money withdrawals, deposits and
  transfers.

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File Processing.

• Report Files
• A file created by extracting data to prepare a
  report
• Example, All accounts sorted by account number
  containing the details like account name, balance
  and so on

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File Processing.

• Operations on Files
• There are mainly two kinds of file operations
• Retrieval and
• Update operations
• Retrieval operations do not change the contents
  of the file thus it only locates records in the
  file matching certain specific criteria
• Update operations change the contents of the file
  by modifying the records, deleting (delete) the
  records and inserting (Insert) new records

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File Processing.

• Operations on Files
• The following five operations are required for
  the processing of records in files
• File creation
• Records location
• Record creation
• Record deletion
• Record modification

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File Processing.

• File Organisation
• A technique for physically arranging the records
  of a file on secondary storage devices
• Factors necessary to be considered when choosing
  the file organisation
• Speed of data retrieval
• Speed of processing data
• Speed of update operations
• Storage space
• Security

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File Processing.

• File organisation..
• Two types of file organisation are
• Sequential file organisation and
• Direct file organisation
• Sequential file organisation
• Records are stored in some predetermined sequence
  one after the other
• It contains one field referred to as Primary Key
• Primary Key usually determines their sequence or
  order

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File Processing.

• Sequential file organisation.
• A primary key is a field ( or set of fields)
  whose contents is unique to one record and can
  therefore be used to identify that record.
• Example, Student_ID, Customer_ID, Emp_ID and so
  on
• Sequential file organisation is very common
  because it makes effective use of the least
  expensive secondary storage device the magnetic
  tape

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File Processing.

• Sequential file organisation.
• Records must be processed and accessed
  sequentially
• It means when using sequential access to reach a
  particular record, all records preceding it most
  first be processed
• Efficient when the entire file or an appreciable
  portion of the file must be processed together
• Processing data using sequential access referred
  to as sequential file processing

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File Processing.

• Advantages of Sequential file processing
• It uses magnetic tape, the least expensive method
  of secondary storage.
• It is the most efficient form of organisation
  when the entire of file or most of it is
  processed at once
• Transaction file and old master file together act
  as a back-up, it can be used to create the new
  master file when existing one damaged or
  destroyed

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File Processing.

• Disadvantages ..
• Time factor the time it takes to access a
  particular record may be too long for many
  applications
• The entire file most be accessed and a new master
  file created , even if only one record requires
  maintenance or updating.

70
Database Management Systems (DBMS)

• Abdallah Seleman
• dullextz_at_gmail.com
• Block D,55
• Consultation Hours
• Tuesday Wednesday
• 1000 AM-1200PM

71
File Processing.

• Advantages of Sequential file processing
• It uses magnetic tape, the least expensive method
  of secondary storage.
• It is the most efficient form of organisation
  when the entire of file or most of it is
  processed at once
• Transaction file and old master file together act
  as a back-up, it can be used to create the new
  master file when existing one damaged or
  destroyed

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File Processing.

• Disadvantages ..
• Time factor the time it takes to access a
  particular record may be too long for many
  applications
• The entire file most be accessed and a new master
  file created , even if only one record requires
  maintenance or updating.

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File Processing.

• Direct File Organisation
• The data can be organised in such a way that they
  are scattered throughout the disk
• This form of organisation that supports direct
  access also referred to as random access
• The records can be accessed nearly
  instantaneously and in any order
• When a record accessed, a record can be read or
  updated and when this process competed , then the
  system is free to respond to another request

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File Processing.

• Direct processing requires either magnetic disk
  or optical disk and cannot use magnetic tape
• Direct access systems do not search the entire
  file rather, they move direct or nearly directly
  to the required record, to do this the system
  must have some way to determine where a
  particular record is stored
• Example, in figure 4, data are entered directly
  into the system through a terminal that is in
  contact with the CPU of the central computer, the
  system locates the specific record in the master
  file and then updates it.

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File Processing.
Figure 4, Direct File Processing Records are accessed directly
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File Processing.

• Direct file processing.
• There are several strategies which are used to
  find record..
• Relative addressing
• Hashing (randomising)
• Indexing
• Relative addressing
• Simplest method of finding a record
• A records primary key is associated with a
  specific physical storage location
• On retrieval process, the user enters the Key and
  the disk operating system associates this key
  with the appropriate location on the disk

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File Processing.

• Relative addressing.
• Relative addressing loses its appeal when the
  record key cannot be made to match the physical
  location
• Hashing also known as Randomising
• Method for determining the physical location of a
  record.
• The record key is processed mathematically and
  another number is computed that represents the
  location where the record will be stored
• Record keys are transformed into storage
  addresses and by using an arithmetic procedures
  called randomising or hashing algorithm

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File Processing.

• The task of this process is to take a set of
  records keys and find a formula to map them into
  set of disk storage location Identifiers
• On retrieval process, user needs to retrieve the
  record once its key is entered and the hashing
  routine is used to determine where the record can
  be found on storage disks.
• Major difficulty with the hashing procedure is
  due to that some addresses will never get
  generated whilst two or more record keys produce
  identical disk address or synonyms or Collisions

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File Processing.

• Indexing
• It uses a primary index which associates a
  primary key with the physical location in which
  a record is stored.
• Advantages of direct file organisation
• Data can be accessed directly and quickly
• Primary and secondary indexes can be used to
  search data in many ways
• Files can still be processed sequentially using
  secondary index
• Centrally maintained data can be kept up-date

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File Processing.

• Disadvantages of direct file processing
• The use of an index lowers the computer systems
  efficiency
• The hardware must be expensive for these systems
  because all data must be stored on disks
• There will be no backup data if a file destroyed,
  the files are updated directly and no transaction
  files are maintained on system

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File Processing.

• Summary on direct file organisation
• The choice of file organisation and the methods
  used for direct access depend on the five
  characteristics
• File volatility
• File activity
• File query needs
• File size
• Data currency

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Data Processing

• Data processing comprises the following
• Capturing of data
• Storing of data
• Updating and retrieving of data and information
• Data Management
• Data management is the arrangement of all data
  and information with an organization
• It also refers to the methods of physical storage
  and retrieval of data on a disk or other storage
  devices

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Data Management..

• Data management involves the following,
• Data administration
• The standards of defining data
• The way in which people perceive and use data in
  their day-to-day activities

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Data Independence

• Data Independence
• Data independence allows a database to be
  structurally changed , it means data can be
• Added and deleted or data attributes altered with
  minimum disruption to the existing system
• This implies that application programs are not
  required to have detailed knowledge of the
  records layout, it means when a record layout is
  changed like fields added, deleted, changed in
  size then fewer application programs or none
  would be changed

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Data Independence.

• There are two distinct levels of data
  independence
• Logical data independence
• Physical data independence
• Logical data independence
• Insulates application programs from logical
  operations such as combining two records into one
  or splitting an existing record into two or more
  records

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Data independence.

• Physical data independence
• Indicates that the physical storage structures or
  devices used for storing data could be changed,
  this happens without needing a change in the
  record structure or application programs

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Database Administration Roles

• Database administration Centrally controlling
  the database
• Implemented by a person or group of persons under
  the supervision of a knowledgeable person called
  Administrator, this person known as Database
  Administrator (DBA)
• DBA is responsible for supervising the creation,
  modification and maintenance of the database

The DBA controls the database structure and sets
up the definition for physical as well as
logical implementation of the database.
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Database Administration Roles..

• Implementing Security Features,
• DBA maintains the integrity of a database
• DBA maintains that the database is not accessible
  by unauthorised users,
• DBA is responsible for granting permission to use
  the database and stores the profile of each user
• The user profile can be used by the DBA to verify
  that a particular user is allowed to access and
  perform a given operation on database within the
  limited time frame

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Database Administration Roles

• Measures Against Data Loss
• DBA is responsible for defining procedures to
  recover data from failures human natural, or
  hardware malfunctioning with minimum loss
• DBMS Users
• The users of a database can be classified
  depending on their degree of expertise or their
  mode of interactions with the DBMS.

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Database Administration Roles

• DBMS Users..
• The user can be classified as..
• Naïve Users
• Online Users
• Application Programmers
• BDAs
• Naïve Users
• Are those users who need not be aware of the
  presence of the database system or any other
  system supporting their usage
• Example, the users of an Automatic Teller
  Machine fall in this category.

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Database Administration Roles

• Naïve Users
• The user is instructed through each step of a
  transaction, user respond by pressing a coded key
  or numeric value
• Operations that can be performed by Naïve user
  are very limited and affect on precise portion of
  the database

Naïve users are end users of the database who work through a menu driven application program where the type and range of response is always indicated to the user ( Jain et al., 2002)
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Database Administration Roles

• Online Users
• Are those users who may communicate with the
  database directly via an online terminal or
  indirectly via a user interface and application
  program
• These users are aware of the presence of the
  database system and may have acquired a certain
  amount of expertise with the limited interaction
  they are permitted with a database

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Database Administration Roles

• Application programmers
• Professional programmers, who are responsible for
  developing application programs or user interface
• Database Administrator
• DBA is a knowledgeable person who is responsible
  for the physical design and management of the
  database

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Data Dictionary

• A Data Dictionary is a database about databases,
  it holds the following information about each
  data element in the databases
• Name
• Type
• Range of values
• Source
• Access authorization
• Indicates which application programs use the
  data.
• A data dictionary may be a stand-alone
  information system used for management and
  documentation purposes, or it may be an integral
  part of the database management system.
• Data dictionary is used to actually control the
  database operations, data integrity and accuracy

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Data Dictionary..

• Importance of Data Dictionary
• It provides the name of a data element, its
  description, and data structure in which may be
  found
• Provides great assistance in producing a report
  of where a data element is used in all programs
  that mention it
• It is possible to search for a data name,
  provided keywords that describe that name

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Database Processing
Figure 1, Components of a Database
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Database processing..

• What is a Database?
• A collection of data designed to be used by
  different people,
• Organised in such a way that a computer program
  can quickly select desired piece of information
• A database consists of four elements
• Data
• Relationships
• Constraints
• Schema
• Data
• Binary computer representations of stored logical
  entities
• They are distinct piece of information usually
  formatted in a special way.
• The term data is often used to distinguish binary
  (machine-readable) information from textual
  (human-readable) information.

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Database Processing.

• Example, some applications make a distinction
  between data files (files that contain binary
  data) and text files (files that contain ASCII
  data)
• In database management systems, data files are
  the files that store the database information
  whereas other index files and data dictionaries,
  stores administrative information known as
  metadata

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Database processing..

• Relationships
• Relationships represent a correspondence between
  the various data elements
• Constraints
• Are predicates that define correct database
  states.
• Schema
• Describes the organisation of data and
  relationships within the database.
• Defines various views of the database for the use
  of the system components of the database
  management system and for the applications
  security as in figure 2

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Database processing..

• Schema
• It separates the physical aspects of data storage
  from the logical aspects of the representation
• As in figure 2,
• The internal schema defines how and where data
  are organised in physical data storage
• The conceptual schema defines the stored data
  structures in terms of the database model used.
• The external schema defines a view/s of the
  database for particular users. In this case the
  database management system provides services for
  accessing the database whilst maintaining the
  required correctness and consistency of the
  stored data

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Database processing..
Figure 2, Organisation of a Database
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Database processing..

• Why a Database
• Why should an organisation have an integrated
  database to store its operational data?
• Deficiencies of pre-database information
  processing include (but not limit to) the
  following
• Data inconsistency
• Lack data integrity
• Data repetition or redundancy
• Interdependence between programs and data files
• Lack of foolproof data security mechanisms
• Lack of coordination across applications using
  common data
• Non-uniform back-up and recovery methods
• Encoded data

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Database processing..

• The advantage of having the data in a database
  are
• Redundancy can be reduced having a centralised
  database redundancy or multiple copies of the
  same data can be reduced
• Inconsistency can be avoided this depends on
  data redundancy, which means when the same data
  is duplicated and changes are made at one site,
  which is not propagated to the other site, then
  it gives rise to inconsistency. So if the
  redundancy is removed chances of having
  inconsistent data is also removed
• Data can be shared the existing application can
  share data in a database
• Standards can be enforced with the central
  control of the database, the DBA can enforce
  standards
• Security restrictions can be applied the DBA can
  define authorisation checks to be carried out
  wherever access to sensitive data is attempted.

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Database processing..

• Integrity can be maintained integrity means that
  the data in the database is accurate. Centralised
  control of the data helps in permitting the
  administrator to define integrity constraints to
  the data in the database
• Conflicting requirement can be balanced database
  designers can be able to create database that is
  the best for the organisation by knowing the
  overall requirements.

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Database processing..

• Characteristics of Data in a Database
• Shared a data in a database are shared among
  different users and applications
• Persistence data in a database exist permanently
  in the sense the data can live beyond the scope
  of the process that created
• Validity/Integrity/ Correctness data should be
  correct with respect to the real world entity
  that they represent
• Security data should be protected from
  unauthorised access
• Consistency whenever more that one data element
  in a database represents related real-world
  values, the values should be consistent with
  respect to the relationship
• Non-Redundancy no two data items in a database
  should represent the same real-world entity
• Independence the three levels in the schema
  (internal, conceptual and external) should be
  independent of each other so that changes in the
  schema at one level should not affect the other
  levels

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Types of Database Language

• There are three types of database languages
• DDL ( Data Definition Language)
• DML (Data Manipulation Language)
• DCL (Data Control Language)

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Types of Database Language

• DDL
• Used to define data and their relationships to
  other types of data
• Used to formulate schema-level concepts
• Mainly used to create files, databases, data
  dictionaries, and tables within databases.
• Defines the format or schema of the database

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Data Definition Language

• It allows specification of following information
  about each tables
• The schema of each table
• The integrity constraints
• The set of values associated with each attribute
• The security and authorization information for
  each table
• The physical storage structure of each table on
  disk

The SQL commands that are used to create database objects are known as Data Definition Language or DDL
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Types of Database Language

• DML
• DML is a language which deals with the processing
  or manipulation of various database objects
• It provides for the program interface to open and
  close database, find records in files, navigate
  through the records, add new records and change
  or delete existing records
• To formulate changes to be effected in a database
  instance

The SQL commands that are used to manipulate data within database objects are called Data Manipulation Language or DML
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Types of Database Language

• DCL
• DCL is a language which used to improve security
  features and thus prevents unauthorised access to
  data in the database
• Security is provided by granting or revoking
  privileges on a user
• Privileges determines whether or not a user can
  execute a given command or a command can be
  executed on specific groups of data

The SQL commands that are used to control the behaviour of database objects are called Data Control Language or DCL
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• Any Questions

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Database Management Systems (DBMS)

• Outline
• Introduction to DBMS
• Database Architecture
• Database Management System
• Why DBMS
• Types of DBMS