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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: – PowerPoint PPT presentation

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  • 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.

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

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
  • A person will use a file number to retrieve it

  • USER

  • 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

  • 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

File processing systems structure
Customer Processing Application
Customer file
Customer file
User 1
Rental file
Rental Processing Application
Rental file
User 2
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
  • Program
  • data independence for file formats and
    access techniques

  • 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

  • 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

  • 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

  • MY SQL

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

  • To provide decision support
  • To provide transaction processing

  • 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

  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

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

  • 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

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

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

  • 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

  • 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

  • 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

  • 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
  • The core of Relational data base model is the
    concept of table, which is also called relation
    in which all data is stored

  • 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

  • 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
  • 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

  • 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
  • Data base design is non deterministic

  • Here the overall database structure is defined.
  • It involves the following tasks
  • 1. The purpose of database is
  • 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

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.

  • 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

  • Relationship
  • A relationship is a connection between entity
  • 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
  • 2. One-to-may
  • 3.Many-to-many
  • Candidate keys

  • 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

  • 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

Database Management Systems (DBMS)
  • Abdallah Seleman
  • Computing and Information Technology Dept.
  • The Institute of Finance Management

Course Co-ordinator
  • Abdallah Seleman
  • Block D,55
  • Consultation Hours
  • Tuesday Wednesday
  • 1000 AM-1200PM

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

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

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

  • 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

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

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

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.

Fundamentals of Database.
Figure 2 illustrates the concepts of Fields, Records, Files and Database
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
  • Telephone directory where subscriber names are
    listed in alphabetic order.
  • Figure 2 shows Employees Database having related
    files containing records of employees

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

File Processing
  • Data, Information, Knowledge

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
  • 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.

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)
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
  • It consists of data , images , text , documents
    and voice often inextricably intertwined but
    always organised in a meaningful context.

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
  • Example, If orders and payments are data, then
    balance_due and quantity_in_hand would be the
  • 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

File Processing.
Figure 3, Information Cycle
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

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.

File Processing.
  • File..
  • It contains data that is needed for information
  • 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.

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
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

File Processing.
  • Master files
  • A file of relatively permanent information about
  • 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

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

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

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

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

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

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

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
  • Sequential file organisation is very common
    because it makes effective use of the least
    expensive secondary storage device the magnetic

File Processing.
  • Sequential file organisation.
  • Records must be processed and accessed
  • 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

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

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

Database Management Systems (DBMS)
  • Abdallah Seleman
  • Block D,55
  • Consultation Hours
  • Tuesday Wednesday
  • 1000 AM-1200PM

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

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

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

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.

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

File Processing.
  • Relative addressing.
  • Relative addressing loses its appeal when the
    record key cannot be made to match the physical
  • Hashing also known as Randomising
  • Method for determining the physical location of a
  • 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

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

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

File Processing.
  • Disadvantages of direct file processing
  • The use of an index lowers the computer systems
  • 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

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

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

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

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

Data Independence.
  • There are two distinct levels of data
  • 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

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

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.
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

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.

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.

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)
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
  • 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

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

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
  • 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

Data Dictionary..
  • Importance of Data Dictionary
  • It provides the name of a data element, its
    description, and data structure in which may be
  • 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

Database Processing
Figure 1, Components of a Database
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
  • 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.

Database Processing.
  • Example, some applications make a distinction
    between data files (files that contain binary
    data) and text files (files that contain ASCII
  • 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

Database processing..
  • Relationships
  • Relationships represent a correspondence between
    the various data elements
  • Constraints
  • Are predicates that define correct database
  • 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

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

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

Database processing..
  • The advantage of having the data in a database
  • 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
  • Security restrictions can be applied the DBA can
    define authorisation checks to be carried out
    wherever access to sensitive data is attempted.

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.

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

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

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

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

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

The SQL commands that are used to manipulate data within database objects are called Data Manipulation Language or DML
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
  • Any Questions

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