Lec-1 Introduction to Databases

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<ul><li><p>8/4/2019 Lec-1 Introduction to Databases</p><p> 1/20</p><p>DATABASE MANAGEMENT SYSTEMS (BIS3103)</p><p> Lecturer: Alice Nandawula Mugisha</p><p> Email: amugisha@cit.mak.ac.ug</p><p> Room: Room 202 (Staff Working Space), Block A</p><p>1</p>mailto:amugisha@cit.mak.ac.ugmailto:amugisha@cit.mak.ac.ug</li><li><p>8/4/2019 Lec-1 Introduction to Databases</p><p> 2/20</p><p>CHAPTER 1Introduction to Databases2</p></li><li><p>8/4/2019 Lec-1 Introduction to Databases</p><p> 3/20</p><p>OBJECTIVES</p><p> Characteristics of file-based systems.</p><p> Problems with file-based approach.</p><p> Meaning of the term database.</p><p> Meaning of the term Database Management System</p><p>(DBMS).</p><p> Typical functions of a DBMS.</p><p> Advantages and disadvantages of DBMSs.</p><p> Some common uses of database systems</p><p>3</p></li><li><p>8/4/2019 Lec-1 Introduction to Databases</p><p> 4/20</p><p>FILE-BASED SYSTEMS</p><p>A file is a collection of records which</p><p>contain logically related data.Collection of application programs that</p><p>perform services for the end users (e.g.</p><p>reports).</p><p>Each program defines and manages its own</p><p>data.</p><p>Better alternative to paper based filing</p><p>systems.4</p></li><li><p>8/4/2019 Lec-1 Introduction to Databases</p><p> 5/20</p><p>5</p><p>FILE-BASED APPROACH</p><p> A system of files and collection of applicationprograms manipulating them is a file-basedsystem</p><p>The UniversitysFile-Based System</p></li><li><p>8/4/2019 Lec-1 Introduction to Databases</p><p> 6/20</p><p>LIMITATIONS OF FILE-BASED APPROACH</p><p> Separation and isolation of data</p><p> Each program maintains its own set of data.</p><p> Users of one program may be unaware of</p><p>potentially useful data held by other programs.</p><p> Duplication of data</p><p> Same data is held by different programs.</p><p>Wasted space and potentially different values and/ordifferent formats for the same item.</p><p>6</p></li><li><p>8/4/2019 Lec-1 Introduction to Databases</p><p> 7/20</p><p>LIMITATIONS OF FILE-BASED</p><p>APPROACH</p><p> Data dependence</p><p> Unhealthy dependency between data and programs.Filestructure is defined in the program code.</p><p>Incompatible file formats Programs are written in different languages, and so</p><p>cannot easily access each others files.</p><p> Fixed Queries/Proliferation of application programs</p><p> Programs are written to satisfy particular functions. Anynew requirement needs a new program.</p><p>7</p></li><li><p>8/4/2019 Lec-1 Introduction to Databases</p><p> 8/20</p><p>DATABASE APPROACH</p><p> Arose because:</p><p> Definition of data was embedded inapplication programs, rather than beingstored separately and independently.</p><p>No control over access and manipulationof data beyond that imposed byapplication programs.</p><p> Therefore there was a need to</p><p>separate data from programs but witha facility for them to interact.</p><p>8</p></li><li><p>8/4/2019 Lec-1 Introduction to Databases</p><p> 9/20</p><p>DATABASE APPROACH</p><p>Result</p><p> the database and Database ManagementSystem (DBMS).</p><p>Databases were therefore developed tostore, organize and secure data whileapplications can be able to access thedatabase, process the data and generatethe required information. 9</p></li><li><p>8/4/2019 Lec-1 Introduction to Databases</p><p> 10/20</p><p>DATABASE</p><p>Shared collection of logically related data (and adescription of this data), designed to meet theinformation needs of an organization.</p><p>System catalog (metadata) provides description ofdata to enable programdata independence.</p><p>Logically related data comprises entities,attributes, and relationships of an organization'sinformation.</p><p>10</p></li><li><p>8/4/2019 Lec-1 Introduction to Databases</p><p> 11/20</p><p>DATABASE APPROACH</p><p> Data definition language (DDL).</p><p>Permits specification of data types, structures and anydata constraints that should be part of the database.</p><p> All specifications are stored in the database.</p><p>Data manipulation language (DML). Enables those with access to the database to insert,</p><p>update, delete and retrieve data from it.</p><p> Standard Query Language (SQL) is an example of a</p><p>DML</p><p>11</p></li><li><p>8/4/2019 Lec-1 Introduction to Databases</p><p> 12/20</p><p>DATABASE ENVIRONMENT PLAYERS</p><p> Data Administrator: Responsible over the data policies in</p><p>the organization. Does not need to be a technical person. Database Administrator: Puts into practice the data</p><p>policies of the organization, like back ups, recovery,</p><p>integrity, security, availability, performance and testing</p><p>support.</p><p> Applications Program Developer: Responsible over</p><p>development of the application programs that make use of</p><p>the data in the database.</p><p> User: Makes use of the information from the applications</p><p>that talk to the database. The user may be novice or</p><p>sophisticated</p><p>12</p></li><li><p>8/4/2019 Lec-1 Introduction to Databases</p><p> 13/20</p><p>DATABASE MANAGEMENT SYSTEM</p><p>(DBMS)</p><p>DBMS: A software system that enables</p><p>users to define, create, and maintain the</p><p>database and which provides controlled</p><p>access to this database.</p><p>Database Application: A computer programthat interacts with the database by issuing an</p><p>appropriate request (typically an SQLstatement) to the DBMS.</p><p>13</p></li><li><p>8/4/2019 Lec-1 Introduction to Databases</p><p> 14/20</p></li><li><p>8/4/2019 Lec-1 Introduction to Databases</p><p> 15/20</p><p>FUNCTIONS OF A DBMS</p><p>Authorization Services.</p><p>Support for Data Communication.</p><p> Integrity Services.</p><p>Services to Promote Data Independence.</p><p>Utility Services.</p><p>15</p></li><li><p>8/4/2019 Lec-1 Introduction to Databases</p><p> 16/20</p><p>ADVANTAGES OF DBMS</p><p>Control of data redundancy</p><p>Data consistency</p><p>More information from the same amount of data.</p><p>Sharing of data Improved data integrity</p><p> Improved security</p><p>Enforcement of standards</p><p>16</p></li><li><p>8/4/2019 Lec-1 Introduction to Databases</p><p> 17/20</p><p>ADVANTAGES OF DBMS</p><p>Balanced conflicting requirements</p><p> Improved data accessibility and responsiveness</p><p> Increased productivity</p><p> Improved maintenance through data independence Increased concurrency</p><p> Improved backup and recovery services</p><p>17</p></li><li><p>8/4/2019 Lec-1 Introduction to Databases</p><p> 18/20</p><p>DISADVANTAGES OF DBMS</p><p> Complexity</p><p> Size</p><p> Cost of DBMS</p><p> Additional hardware costs Cost of conversion</p><p> Performance</p><p> Higher impact of a failure</p><p>18</p></li><li><p>8/4/2019 Lec-1 Introduction to Databases</p><p> 19/20</p><p>DATA BASE MODELS</p><p> A database model is an organizational principleused in organizing data by a databasemanagement system.</p><p> Different database management systems of thesame model have the same principle of dataorganization. e.g. MS Access, Oracle and MicrosoftSQL server use tables (relations) to organize thedata.</p><p> They are 'Relational' database managementsystems.</p><p>19</p></li><li><p>8/4/2019 Lec-1 Introduction to Databases</p><p> 20/20</p><p>TYPES OF DATABASE MODELS The Network Model: Represents data as nodes and</p><p>relationships are implied by linking up the nodes by</p><p>edges. The Hierarchical Model: Represents data and nodes</p><p>in a hierarchical manner.</p><p> The Deductive Model: Represents minimal data as'Axioms'. Extra data and relationships are deduced.</p><p> The Relational Model: Uses relations/table toorganize data. A row/tuple represents an instance ofdata and relationships are represented by foreignkeys.</p><p> The Object Oriented Model: Uses the objectoriented paradigm of encapsulation, inheritance andpolymorphism. A class represents data and an objectrepresents the instance.</p><p>20</p></li></ul>