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 Program A Program B Program C Program A Program B Program A Program B Order Filing System Invoicing System Payroll System Customer Master File Inventory Master File Back Order File Inventory Pricing File Customer Master File Employee Master 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

Example STUDENTNameStudentNumberClassMajor Smith171CS Brown82CS COURSECourseNameCourseNumberCreditHoursDepartment Discrete MathematicsMATH24103MATH DatabaseCS33804CS SECTIONSectionIDentifierCourseNumberSemesterYear 85MATH2410Fall03 135CS3380Fall04 Instructor Anderson Stone GRADE_REPORTStudentNumber 17 SectionIDentifier Grade A B 8135A PREREQUISITECourseNumber MATH222 CS3380 PrerequisiteNumber MATH211 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