Lecture Database management systems Chapter 1 Overview of database management system

Chapter 1 Overview of database management system. This chapter includes contents Overview of database management systems (DBMS), an example, characteristics of the database, DBMS vs. filebased system, advantages of using the DBMS approach.

Chapter 1

Overview of Database Management System

Data and Information

 Data:

◦ Raw facts that constitute building block of information

◦ The heart of the DBMS

 All the data will not convey useful

information

 Data Information processed

Collection of information metadata

Data

Database

 A database:

◦ A collection of data that are related in a meaningful way, which can be accessed in different logical orders

 The main features of the data in the

Database example

 Book airline ticket

 Register a new course in university

 Buy book in the bookstore

 Library management

 …

Database

Simplified database view

Database Management System

 DBMS

◦ A general purpose software package designed

to store and manage database

 DBMS is helpful in maintaining and

utilizing a database

Database Management System

Capabilities of database management system

Data dictionary

 Data dictionary or “system catalog”

◦ A centralized store of information about the database

◦ Contain information about the tables, the

fields the tables contain, data types, primary keys, indexes, the joins which have been

established between those tables, referential integrity, cascades update, cascade delete, etc

Database Models

 A collection of tools for describing the

database (include data, relationships,

sematics, constraints) at a level of abstraction

 Levels of abstraction:

◦ Conceptual Data Model:

 a high level description useful for requirements

understanding

◦ Representational Data Model

 describing the logical representation of data without

giving details of physical representation

◦ Physical Data Model

 description giving details about record formats,file

structures etc

The University Database

 The University Database Context: maintaining information concerning students, courses, and grades in a university environment

 STUDENT file stores data on each student

 COURSE file stores data on each course

 SECTION file stores data on each section of

Objectives

 Overview of DBMS

 An Example

 Characteristics of the Database

 Advantages of using the DBMS approach

Database Management System

 Objectives of DBMS:

◦ Data availability: users can easily access the

data

◦ Data integrity: the data available in the

database is a reliable data

◦ Data security: only authorized users can

access the data Data security can be enforced

by passwords

◦ Data Independence: DBMS allows the user to

store, update, and retrieve data in an efficient manner

File-Based System vs DBMS

 Duplication of data: same data being stored

more than once

 Data dependence: the application program

depends on the data

 Incompatible file formats: the structure of

the file depends on the application

programming language

 Separation, and isolation of data: must

synchronize the processing of two files to ensure that the correct data are extracted If data has to be retrieved from more than two files  difficult to access

The levels of data abstraction

The levels of data abstraction

 Physical level or internal level:

◦ the physical storage of the information

◦ complex low-level data structures in detail

 Logical level or conceptual level:

◦ describes what data are stored in the database and

what relationships exist among those data

◦ the entire database in terms of a small number of

simple structures

 View level or external level:

◦ the highest level of abstraction It is the view that the individual user of the database has

◦ There can be many view level abstractions of the same data

People Interacting with Database

Objectives

 Overview of DBMS

 An Example

 Characteristics of the Database

 Advantages of using the DBMS approach

Advantages of DBMS

 Centralized data management:

and data structures

 Data Independence:

the data are structured and stored

application programs and the data

◦ Restricting unauthorized access

 Providing multiple user interfaces

Summary

 The main objective of database

management system is to store and

manipulate the data in an efficient manner

 A database is an organized collection of

related data

 All the data will not give useful

information Only processed data gives

useful information, which helps an

organization to take important decisions