Dbms1

1,775 views
1,596 views

Published on

DATA BASE MANAGEMENT SYSTEM

Published in: Technology
0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total views
1,775
On SlideShare
0
From Embeds
0
Number of Embeds
3
Actions
Shares
0
Downloads
32
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide
  • 3
  • 5
  • 7
  • 6
  • 22
  • Dbms1

    1. 1. What Is a DBMS? <ul><li>A very large, integrated collection of data. </li></ul><ul><li>Models real-world enterprise. </li></ul><ul><ul><li>Entities (e.g., students, courses) </li></ul></ul><ul><ul><li>Relationships (e.g., John is taking C ENG302 ) </li></ul></ul><ul><li>A Database Management System (DBMS) is a software package designed to store and manage databases. </li></ul>
    2. 2. Why Study Databases?? <ul><li>Shift from computation to information </li></ul><ul><li>Datasets increasing in diversity and volume. </li></ul><ul><ul><li>Digital libraries, interactive video, EOS project </li></ul></ul><ul><ul><li>... need for DBMS exploding </li></ul></ul><ul><li>DBMS encompasses most of CS </li></ul><ul><ul><li>OS, languages, theory, “AI”, multimedia, logic </li></ul></ul>?
    3. 3. Why Use a DBMS? <ul><li>Data independence and efficient access. </li></ul><ul><li>Reduced application development time. </li></ul><ul><li>Data integrity and security. </li></ul><ul><li>Uniform data administration. </li></ul><ul><li>Concurrent access, recovery from crashes. </li></ul>
    4. 4. Data Models <ul><li>A data model is a collection of concepts for describing data. </li></ul><ul><li>A schema is a description of a particular collection of data, using the given data model. </li></ul><ul><li>The relational model of data is the most widely used model today. </li></ul><ul><ul><li>Main concept: relation , basically a table with rows and columns. </li></ul></ul><ul><ul><li>Every relation has a schema , which describes the columns, or fields. </li></ul></ul>
    5. 5. Example: University Database <ul><li>Conceptual schema: </li></ul><ul><ul><li>Students(sid: string, name: string, login: string, </li></ul></ul><ul><ul><li> age: integer, gpa:real) </li></ul></ul><ul><ul><li>Courses(cid: string, cname:string, credits:integer) </li></ul></ul><ul><ul><li>Enrolled(sid:string, cid:string, grade:string) </li></ul></ul><ul><li>Physical schema: </li></ul><ul><ul><li>Relations stored as unordered files. </li></ul></ul><ul><ul><li>Index on first column of Students. </li></ul></ul><ul><li>External Schema (View): </li></ul><ul><ul><li>Course_info(cid:string,enrollment:integer) </li></ul></ul>
    6. 6. Instance of Students Relation <ul><ul><li>Students ( sid : string, name: string, login: string, </li></ul></ul><ul><ul><li>age: integer, gpa: real ) </li></ul></ul><ul><ul><li>sid name login age gpa </li></ul></ul><ul><ul><li>53666 Jones [email_address] 18 3.4 </li></ul></ul><ul><ul><li>53688 Smith [email_address] 18 3.2 </li></ul></ul><ul><ul><li>53650 Smith [email_address] 19 3.8 </li></ul></ul>
    7. 7. Levels of Abstraction <ul><li>Many external schemata , single conceptual(logical) schema and physical schema . </li></ul><ul><ul><li>External schemata describe how users see the data. </li></ul></ul><ul><ul><li>Conceptual schema defines logical structure </li></ul></ul><ul><ul><li>Physical schema describes the files and indexes used. </li></ul></ul><ul><li>Schemas are defined using DDL; data is modified/queried using DML . </li></ul>Physical Schema Conceptual Schema External Schema 1 External Schema 3 External Schema 2
    8. 8. Data Independence <ul><li>Applications insulated from how data is structured and stored. </li></ul><ul><li>Logical data independence : Protection from changes in logical structure of data. </li></ul><ul><li>Physical data independence : Protection from changes in physical structure of data. </li></ul><ul><li>One of the most important benefits of using a DBMS! </li></ul>
    9. 9. Data Independence <ul><li>Techniques that allow data to be changed without affecting the applications that process it. There are two kinds of data independence. The first type is data independence for data, which is accomplished in a database management system (DBMS). It allows the database to be structurally changed without affecting most existing programs. Programs access data in a DBMS by field and are concerned with only the data fields they use, not the format of the complete record. Thus, when the record layout is updated (fields added, deleted or changed in size), the only programs that must be changed are those that use those new fields. </li></ul>
    10. 10. Structure of a DBMS <ul><li>A typical DBMS has a layered architecture. </li></ul><ul><li>This is one of several possible architectures; each system has its own variations. </li></ul>These layers must consider concurrency control and recovery Query Optimization and Execution Relational Operators Files and Access Methods Buffer Management Disk Space Management DB

    ×