Database

Database

1. • Communications systems • Transportation and logistics • Financial management • Knowledge-based systems • Accessibility to scientific literature • A host of other civilian • Defense applications.

2. • Developments in hardware capability • Hardware capacity • Communications • Internet • Electronic commerce • Business intelligence • Mobile communications • Grid computing.

3. Common applications

   • - Purchases from the supermarket. -Purchases using your credit card. -Booking a holiday at the travel agents. -Using the local library.

4. File: collection of records. It contains logically related data.

   • File-Based Approach
   • Limitations
     • Separation and isolation of data: difficulty to access data
     • Duplication of data: wasteful, it cost time, money and additional storage space
       • Avoided by sharing data files.
     • Program-Data dependence
     • Incompatible file formats: dependency on the application programming language
     • Fixed queries/proliferation of application programs

5. Features

   • Large repository of data, simultaneously use, integrated data with minimum amount of duplication, self-describing collection of integrated records
     • System catalog: It describes the nature of the data
     • Data abstraction: We can change the internal definition of an object without affect- ing the users of the object.
     • Entity: distinct object that is to be represented in the database
     • Attribute: Property that describes some aspect of the object
     • Relationship: Association between entities

6. DBMS

   • "Software that interacts with the users’ application programs and the database"
   • Define database
   • Insert, update, delete, and retrieve by a Data Manipulation Language (DML).
   • Provides controlled access
   • Hardware
   • Software
   • Data
   • Procedures
   • People
     • -Data and database administrators
       • Management and control of a DBMS and its data.
     • Database Designers
       • -Logical database designers
         • Identifies the data, the relationships between the data, and the constraints on the data that is to be stored in the database.
       • -Physical database designers.
         • Decides how the logical database design is to be physic- ally realized.
     • Application Developers
       • They implement the application programs that provide the required functionality for the end-users
     • End-Users
       • The final "clients" of the database
         • Naïve users
         • Sophisticated users
   • Advantages
     • •Control of data redundancy •Data consistency •More information from the same amount of data •Sharing of data •Improved data integrity •Improved security •Enforcement of standards •Economy of scale •Balance of conflicting requirements •Improved data accessibility and responsiveness •Increased productivity •Improved maintenance through data independence •Increased concurrency •Improved backup and recovery services
   • Disadvantages
     • •Complexity •Size •Cost of DBMSs •Additional hardware costs •Cost of conversion •Performance •Higher impact of a failure

7. Definition

   • Collection of related data
     • Database Management System(DBMS): software that manages and control access to the databse
       • Database System: collection of application programs that interact with the database along with the DBMS and database itself.

8. Application programs

   • It´s used to create and maintain the database and to generate information.
   • View mechanism: Allows the user to have his own view of the database
   • Views control the data that should be seen or not.
   • Views control the appearance of the data