King saud university

Introduction to Database Systems

(Chapter 1: Databases and Database Users)

Introducion

Simple exampels : how big institutions work

State Before - File Processing System• In the early days, database applications were built on top of file systems.

State Before - File Processing System

ProgramA

ProgramB

ProgramC

ProgramA

ProgramB

ProgramA

ProgramB

Order Filing System

InvoicingSystem

PayrollSystem

CustomerMaster

File

InventoryMaster

File

BackOrderFile

InventoryPricing

File

CustomerMaster

File

EmployeeMaster

File

Orders Department Accounting Department Payroll Department

Drawbacks of the File Processing System

• Data redundancy (Duplication of data) :• Different systems/programs have separate copies of the same data.

• Limited data sharing:

• No centralized control of data.

• Lengthy development times:• Programmers must design their own file formats.

• Excessive Program maintenance:• 80% of information systems budget.

Solution• A single repository of data should be maintained that is defined once and then accessed by various users (i.e. Database approach).

Introduction to Databases• Databases touch all aspects of our lives.

• Examples:• Banking: all transactions.• Hotels: reservation.• Airlines: reservation, schedules.• Libraries: catalog.• Universities: registration, grades.• Sales: customers, products, purchases.• Manufacturing: production, inventory, orders.• Human resources: employee records, salaries.

Traditional database applications Most of the information is either textual or numeric.

What is a Database?• A collection of related data. stored in a computer system

• Has the following implicit properties:•Is designed for specific purpose and intended users.• Can be at varying size and complexity.• Can be generated and maintained manually or it may be computerized.

Known facts that can be recorded and that have implicit meaning. E.g. names, telephone numbers, addresses.

What is a Database Management System (DBMS)? • A collection of programs that enables users to create and maintain a database.

• Facilitates the process of:• Defining: specifying data types, structures, & constraints for data.•Manipulating: querying the database to retrieve or update data and generating reports from the data.• Sharing: accessing the database concurrently.• Protects the database and maintains it over a long period of time.

• Examples: Oracle, MS Access, DB2, Informix, MySQL, SyBase.

Advantages of Using DBMS• Controlling redundancy in:

• data storage• development and maintenance efforts.

• Sharing of data among multiple users.

• Restricting unauthorized access to data.

What is a Database System?• Is the combination of the database and the DBMS software.

All databases is held in the form of Tables ,each table holding information on a single subject

Each line of a table represents a Record consists of items of data that belong together ( name,student number,class,major)

Each item of data within a record is held in a separate column of the table known as Field

Queries allow questions to be asked of the data and display only the information required. It can include info from more the one table

ExampleSTUDENT Name StudentNumber Class Major

Smith 17 1 CSBrown 8 2 CS

COURSE CourseName CourseNumber CreditHours DepartmentDiscrete Mathematics MATH2410 3 MATHDatabase CS3380 4 CS

SECTION SectionIDentifier CourseNumber Semester Year85 MATH2410 Fall 03

135 CS3380 Fall 04

InstructorAnderson

Stone

GRADE_REPORT StudentNumber1717

SectionIDentifier85

135

GradeAB

8 135 A

PREREQUISITE CourseNumberMATH222

CS3380

PrerequisiteNumberMATH211

CS210

Record

Field

People working with databases Database designer: design and creates a database

suited to the needs of an organization Database administrator: controls the access to different

data for specific users and recovers a database after “crashes”

Database user: enters and maintains(updates)data and retrieves information