◄UNIT 4: E COMMERCE, SOCIAL MEDIA AND ONLINE SERVICESASSESSMENT►

UNIT 5: DATABASE Basics

  • UNIT 5: DATABASE Basics

    5.0 INTRODUCTORY ACTIVITY


    5.1: Introduction to Database


    5.1.1 Definition of Database
    A database is an organized collection of related data.
    It is considered to be organized because the data is stored in categories that are accessible in
    a logical manner. A database is a collection of one or more relations, where each relation is a
    table made of rows and columns.
    5.1.2 Definition of Data and Information
    Data is commonly referred to as ‘raw’ data: a collection of text, numbers and symbols,
               images with no meaning.
               Data therefore has to be processed, or provided with a context, before it can have meaning.
    Information  is the result of processing data, usually by computer.
    This results in facts, which enables the processed data to be used in context and have
    meaning. Information is data that has meaning.

    Note: An information system is a combination of computer hardware and software that is
    designed to create, store, process and present information. The heart of all information
    systems is a database. 


    5.2 Database Approach


    The most efficient way to store data is with the help of a database. A database is made up of
    tables that contain columns and rows. Each category is given its's own table.

    For example: a company may have a table for customer information and another for sales
    numbers. You can think of a table somewhat like a spreadsheet. Inside a spreadsheet there 
    are columns and rows of data. For a database however each row is called a record and each
    cell is called a field.

    5.2.1: Traditional File Processing Systems (TFP) approach

    This is an approach which was used earlier, prior to DBMS. With this approach, users had to
    write their application programs to store data in form of files on the computer permanent
    storage device (Hard Disk). A user must have knowledge of programming languages but this
    is not easy for a common computer user, even an experienced programmer would find it
    difficult to write a program each time a new database was to be created. Each application
    program written by a user had to define and manage its own data. 

    a. Advantages of the Traditional File Processing 
    Compared to manual management of information, the Traditional File Processing presents
    the following advantages:
    Simplicity: the design of file processing is more simple than designing Database
     Efficiency: file processing cost less and can be more speed than Database
     Customization: you can customize file processing more easily and efficiently than
    Database because files are related with the application and it have all the data needed
    for that application. 
    b. Disadvantages of Traditional File Processing System
    Separation and Isolation of Data: In file-based approach, data are isolated in separate files.
     Hence it is difficult to access it.

                                             

      Duplication of Data: Duplication of data means same data being stored more than
                  once. This can also be termed as data redundancy. 
                Wastage of storage space: Duplication of data leads to wastage of storage space.
                 If the storage space is wasted it will have a direct impact on cost. The cost will increase.

          Loss of data integrity: Data integrity means that the data contained in the database is
               both accurate and consistent (Data inconsistency means different copies of the same
              data will have different values).

          Data Dependence: In traditional file processing, the structure of data files is
               embedded in the application programs, so any changes to the structure of a file may
               require changing all programs that access this file. 

           Security problems: File based approach is not secured because different files are
                 stored in different locations

    5.2.2 Database Management System (DBMS)
    The Database Management system (DBMS) is a referred to as a software system that is used
    to store, access, manage, organize, maintain, modify and delete data from databases. Some
    of the most popular software include, Microsoft Access, Oracle, Microsoft SQL Server,
    MySQL.
    MySQL is, one of the most popular database management systems used by online
    entrepreneurs. 


    a. The advantages of database management system
    There are many advantages of database management system.





    5.3 Area where database can be applied

    These days, the evolution of Database management systems has obliged governments, NGOs,
    and private companies to use databases in their daily basics. They are getting more from their
    work because they can keep records of everything.

    Database management systems make these organizations work faster to search for
    information and records about any people or products that make them more effective in
    work. Below are some of the applications and uses of the database management system
    (DBMS).




    5.4 Database Access Levels and Users


    5.4.1 Database access levels
    A major purpose of a database system is to provide users with an abstract view of the data.
    That is, the system hides certain details of how the data are stored and maintained.
    There are three-levels that form the basis of modern database architectures:
    a. The Internal Level
    The Internal level has an internal schema, which describes the physical storage structure of
    the database. The internal schema uses a physical data model and describes the complete
    details of data storage and access paths for the database.
    b. The conceptual level
    The conceptual level has a conceptual schema, which describes the structure of the whole
    database for a community of users.
    The conceptual schema hides the details of physical storage structures and concentrates on
    describing entities, data types, relationships, user operations, and constraints.
    Usually, a representational data model is used to describe the conceptual schema when a
    database system is implemented. This implementation conceptual schema is often based on
    a conceptual schema design in a high-level data model.
    c. The external or view level:
    The external view level is closest to the users. It is concerned with the way the data is viewed
    by individual users. A user can either be an application programmer or an end-user. The
    external level consists of many different external views of database.
    At the view level, computer users see a set of application programs that hide details of the
    data types.

    5.4.2 Database users

    The purpose of the three-level architecture is to separate the user application and the physical
    database. The reasons of this separation are that different users need different views of the
    same data.
    1. Users should not have to deal directly with the physical database storage details.
    2. The database administrator should be able to change the database storage structure
    or storage device without affecting other user's views.
    When considering users of a Database system, there are three broad classes to consider:
    1. The database administrator (DBA): Responsible for authorizing access to the
    database, for coordinating and monitoring its use, acquiring software and hardware
    resources, controlling its use and monitoring efficiency of operations.
    2. The database designer: Responsible to define the content, the structure, the
    constraints, and functions or transactions against the database. They must
    communicate with the end-users and understand their needs.
    3. The end-user, who accesses: End-users, they use the data for queries, reports and
    some of them update the database content.

    5.4.3 Data Independence

    Data Independence: The ability to modify a scheme definition in one level without affecting
    a scheme definition in a higher level is called data independence.
    There are two kinds:
    1. Logical data independence
    The ability to modify the conceptual scheme without causing application programs to be
    rewritten.
    Immunity of external schemas to changes in the conceptual schema usually done when logical
    structure of database is altered.
    2. Physical data independence
    The ability to modify the internal scheme without having to change the conceptual or external
    schemas. 

    Modifications at this level are usually to improve performance.

    5.5 Relational Model


    5.5.1 Definition of Relational Database Model
    The Relational Database Model represents the database as a collection of relations.

    A relation is nothing but a table of values. 

    Every row in the table represents a collection of related data values.
    These rows in the table denote a real-world entity or relationship.
    The table name and column names are helpful to interpret the meaning of values in
            each row. The data are represented as a set of relations. In the relational model, data
            are stored as tables. 

    5.5.2 Relational Model Concepts in DBMS
    Entity is a real-world object that has certain properties called attributes that define
    the nature of the entity.
    In Relational model an entity is considered as table. Entities are distinguishable, i.e., each
    entity in a pair of entities has a property that makes one entity different from the other entity.
    Entities consist of attributes that define their characteristic features/properties.

    For example: if we consider a black piece entity on a chessboard and a white piece on a
    chessboard, they are distinguishable since the color of the black piece and the white piece

    are distinguishable.

    Primary Key is also called a primary keyword, is a key (column) in a relational database
           that is unique for each record.
    Foreign Key is a set of attributes (columns) in a table that refers to the primary key of

           another table.

    Alternate Keys is a column or group of columns in a table that uniquely identify

           every row in that table.

    A table can have multiple choices for a primary key but only one can be set as the primary

    key. All the keys which are not primary key are called an Alternate Key.

     Table: In the Relational model, the relation is saved in the table format.

    A table has two properties rows and columns. Rows represent records and columns represent
    attributes. Table is a named relational database data set that is organized by rows and

    columns.

    Attribute: Each column in a Table. Attributes are the properties which define a relation. 

    Constraint: In DBMS is the set of rules that ensures that when an authorized user

    modifies the database they do not disturb the data consistency.

    Tuple: It is nothing but a single row of a table, which contains a single record.

    Degree: is the total number of attributes which in the relation is called the degree of
    the relation.
    Cardinality: is the total number of rows present in the table.
    Column: The column represents the set of values for a specific attribute.

    

    ◄UNIT 4: E COMMERCE, SOCIAL MEDIA AND ONLINE SERVICESASSESSMENT►