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Note for Database Systems - DS By Saroj Kumar Sahoo

  • Database Systems - DS
  • Note
  • Government College of Engineering Kalahandi - GCEK
  • Computer Science Engineering
  • 5 Topics
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Saroj Kumar Sahoo
Saroj Kumar Sahoo
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DATABASE SYSTEM Contents 1. Introduction to database system 2. Advantages of database system over traditional file system 3. Basic concepts and Definitions 4. Database users 5. Database language 6. Database system Architecture, 7. Schemas, subschemas and instances 8. Database constraints 9. 3-level database architecture 10. Data abstraction 11. Data independence 12. Mappings, Structures 13. Components and functions of DBMS 14. Data Models

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Introduction to Database system 1) Data:The name given to basic facts and entries such as name, Nos etc. 2) Information:The collection of data that has been concerned into more useful (or) intelligible form. 3) Knowledge:Informational containing wisdom is knowledge. *Need of Information: The info is needed to gain knowledge about the surroundings and whatever happening in the society as well as universe.  To keep the system up-to-date.  To know the rules and regulations of the society and the laws of the society.  Based on above 3 correct arise a particular decision for planning correct and prospective access in the process of forming Running and protecting the process or a system. *Need of knowledge: fact based knowledge:The knowledge gained from fundamentals and through the experiment and also there knowledge is derived from info’s containing the fundamental science through some experiments, rules and regulations commonly agreed by the experts.  Heuristic based knowledge:In this case the knowledge of good practice, experience and good judgement like hypothesis and it is the knowledge underline expertise rules of thumb, rules of good grossing that usually achieved desired results but doesn’t guarantee them. Data Information  Data is significant to a business or itself.  It is significant to business or us.  e.g. : Age- 23  e.g. : Age of a person is 23   Attempt level of information.  Doesn’t help in decision making. Collection of Data.  Helps for taking decision.

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Database:The related information placed in an organised form is called Database. e.g.-: Dictionary, telephone directory. New of Database: DB is a collection of inter related data stored together to solve multiple application.  Add new information.  View (or) retrieve (or) Access of stored information.  Modify / edit the existing information.  Delete/remove the unwanted or redundant data/information.  Arranging of information in designed order. Database Approach:Two types :- 1) Manual Approach/file-based Approach 2) Database Approach Disadvantages: separated and isolated data:To make a decision a user need the data from two separated files.  Duplication of data: Data dependence:The files and records were described by a specific physical format that are coded into application program. If the format of the certain record is changed then code for each file must be updated.  Difficulties in representing data in the users view. i.e. to create useful application for user data from various file must be combined.  Data inflexibility :Data interdependency and data isolation limited the flexibility of file processing system providing user with adopt information.  incompatible file format:Structure of file embedded in application program then the structure are dependent on the application programming languages.  integrity problem:All the above approaches are integrating.  Conqueror problem/ accessibility: security DATABASE APPROACH:-

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A database is a shared collection of logically related data, designed to the information need of the organisation  Shared: - All info/data shared are different (or) for different application.  Persistence: - All the data are stored in DB permanently exists.  Validity /integrity/correctness: - The data should be correct with respect to the real world entity.  Security:-The data should be protected from unauthorised access.  consistency  Non-redundant:-Unique data, non-duplicate data.  Independency:-The data of different level should be independent of each other company, the changes in one level should not affect others. DBMS:It is database management system. A system that allows user to create, define, maintain a database and provides control access to data. OR DBMS is a collection of program that enable users to store, modify, extract/ retrieve the information from DB. Ex: - Ms Access, oracle etc. Advantage of DBMS over file system There are several advantages of Database management system over file system. Few of them are as followings:  Controlling Data Redundancy.  Sharing Of Data.  Data Consistency.  Integration of Data.  Integration Constraints.  Data Security  Report Writers.  Control over Concurrency.

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