Csci455ch1, Lecture notes of Fundamentals of E-Commerce

Download Csci455ch1 and more Lecture notes Fundamentals of E-Commerce in PDF only on Docsity!

Csci 455

Csci 455

Chapter 1

Databases and Database Users

Objectives

Objectives

Introduction

Example of database systems

Database characteristics

People associated with database

Advantage of Using a DBMS

Database implications

When Not to use a DBMS

Core Database

Core Database

Terminologies: 1

Terminologies: 1



Data?

Any information (most likely in electronic

form) worth preserving



E.g., names, addresses, grades, etc.



Database?

A collection of related data describing the

activities of one or more organizations

◦ Organized (or structured) for access and

modification

◦ Preserved over a long period



E.g. University Database

Core Terminologies: 3

Core Terminologies: 3



Query?



an operation that extracts specified data

from the database



E.g.



get the list of all courses and grades taken by “Smith”



Relation?



an organization of data into a two-

dimensional table,



rows (tuples) represent basic entities or facts of some sort



columns (attributes or fields) represent properties of those

entities.



Schema?



a description of the structure of the data in

a database



also known as metadata

Database Construction

Database Construction

Database can be constructed

◦

Manually

E.g., a library card catalog

◦

Computerized system

Specialized DB:



A Specific set of applications

General Purpose DB:



Database Mgt systems

Database Mgt system

Database Mgt system

(DBMS)

(DBMS)



Database management system (DBMS)?

◦ A collection of programs that enables

users



To define (specifying data type, etc.)



To construct (storing)



To manipulate (reading, writing)



To share (simultaneous access)



To protect (security & privacy protection)



To modify (changing requirements)



Database System= DBMS + Database

Example: University

Example: University

Database System

Database System

A typical university database

system maintaining information

regarding

◦

Students

◦ Courses

◦ Grade_Report

◦

Section

◦

Prerequisite

Example: A University

Example: A University

Database

Database

Main Characteristics of DB

Main Characteristics of DB



Self-Describing nature of a database

system ( catalog =Data + metadata)



Insulation between programs and

data (program-data-independence)



Support of multiple views of the data

(virtual data)



Sharing of data and multi-user

transaction processing (concurrency

control)

Transaction and atomicity



ACID

People involved in

People involved in

Database

Database

Involved two types of people

◦

people on the Scene

◦

people behind the Scene

People behind the Scene

People behind the Scene

DBMS system designers and

implementers

Tool developers

Operators and maintenance

personnel

File System vs. Database

File System vs. Database

Mgt Systems

Mgt Systems

Suppose an organization needs

to manage a large collection of

data, say, 500 GB (i.e., 500X

MB)

Data is supposed to be accessed

concurrently by employees

Changes made to the data must

be applied consistently

Access to the data must be

restricted

Primary Advantages of Using

Primary Advantages of Using

a DBMS: 1

a DBMS: 1



Controlling Redundancy

Duplicate space and efforts

inconsistency



Restricting Unauthorized Access

Security and authorization subsystem



Providing persistent storage for program

objects and data structure

Impedance mismatch problem

(incompatibility between PL and DBMS)



Deriving new information from existing ones

(view)

Primary Advantages of Using

Primary Advantages of Using

a DBMS: 2

a DBMS: 2



Providing Multiple User Interfaces



Representing Complex Relationships among

Data



Enforcing Integrity Constraints



Providing Backup and crash Recovery



Scheduling concurrent accesses to the data



Reducing application development time