Summary Of Db

Database Management Systems

Chapter 1 Summary of Chapter I

Introduction To The COURSE How Can We Describe A Real-world Enterprise? What Factors Must Be Considered In Deciding

How To Organize The Store Data How can user answer questions about the enterprise by posing queries over the data in the DBMS? How Does A DBMS Store Large Datasets And Answer Questions Against This Data Efficiently?

Teaching and Learning Includes theory and practical sessions Interactive discussions at the end of each

session through Review question (Group or Individual) May require to solve some practical questions

Assessments Includes theory and Practical examination Includes 2 tests and assignment during the

course Final Examination: Practical and theory at the end of the course Total points : 200 Total Credit hours : 4

Today’s Session What is a DBMS, in particular a Relational

DBMS? Why should we consider a DBMS to manage data? How is data in a DBMS retrieved and manipulated? How DBMS support concurrent access and protect data during system failures? Components of A DBMS Who is involved with databases in the real world?

A very large, integrated collection of data. Models real-world enterprise. _ Entities (e.g., students, courses) _ Relationships (e.g., Madonna is taking CS564) A Database Management System (DBMS) is a

software package designed to store and manage databases “Assists in maintaining and utilizing the large collection of data”

Why Use a DBMS? Data independence and efficient access. Reduced application development time. Data integrity and security. Uniform data administration. Concurrent access, recovery from crash

Recovery Reduced application development time

Data Models A data model is a collection of concepts for

describing data. A schema is a description of a particular collection of data, using the a given data model. The relational model of data is the most widely used model today. _ Main concept: relation, basically a table with rows and columns. _ Every relation has a schema, which describes the

Example: University Database

Conceptual schema:

Students(sid: string, name: string, login: string, age: integer, gpa:real) _ Courses(cid: string, cname:string, credits:integer) _ Enrolled(sid:string, cid:string, grade:string) _

Physical schema:

Relations stored as unordered files. _ Index on first column of Students. _

External Schema (View):

_

Course_info(cid:string,enrollment:integer

Databases make these folks happy ... End users and DBMS vendors DB application programmers _ E.g. smart webmasters Database administrator (DBA) _ Designs logical /physical schemas _ Handles security and authorization _ Data availability, crash recovery _ Database tuning as needs evolve