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Databases

Lecture Objectives

-^ Integrated File Approach for saving data^ – Benefits/ Drawback •^ Database Accessing Approach^ – File based Programs– DBMS based access •^ Introducing DBMS^ – Working of a basic DBMS– Main DBMS Features •^ Users in a DBMS Environment

Integrated File Database Example • A Student Grade Database

-^ STUDENT – saving only student personal information•^ GRADE_REPORT – saving only grade information aboutstudent courses – The process which decompose data optimally among datafiles is called

Normalization

STUDENT

Name^

StudentNumber

Class^

Major

Smith^

17

1 CS

Brown^

8

2 CS

GRADE_REPORT

StudentID

CourseCode

SectionCode

Grade

17 MATH

1 B

17 CS

1 C

8 MATH

2 A

8 CS

1 A

8 CS

1 B

8 CS

1 A

…Integrated File Database Example • For detailed information,

a cross-referencing activity is needed

-^ While reading GRADE_REPORT, other student details can be found byusing the data pointer (StudentNumber) in the STUDENT file • Data updation anomalies are removed –^ Addition Anomaly

: While adding a new student’s grade in

GRADE_REPORT file, no need to check for any data consistency. – Deletion Anomaly

: Deleting all grades for any student, doesn’t delete the

student information from STUDENT file. – Modification Anomaly

: A student’s attribute change in STUDENT file (like

Name) doesn’t need to be reflected in his grade records in GRADE_REPORTfile (key attribute is an exception).

STUDENT^

Name^

StudentNumber

Class^

Major

Smith^

17

1 CS

Brown^

8

2 CS

GRADE_REPORT

StudentID

CourseCode

SectionCode

Grade 17 MATH

1 B 17 CS^

1 C 8 MATH^

2 A 8 CS^

1 A 8 CS^

1 B 8 CS^

1 A

1. File Based Application

Programs

AccountingApplication

RegistrationApplication

Any otherapplication….

AccountingEnd User

RegistrationEnd User

Other EndUsers…

Disk Storage STUDENT^ Name^

StudentNumber^ Class

Major Smith^

17 1 CS Brown^

8 2 CS Smith^

8 3 CS Brown^

2 4 CS Smith^

2 5 CS Brown^

2 6 CS

Disk Storage STUDENT^ Name^

StudentNumber^ Class

Major Smith^

17 1 CS Brown^

8 2 CS Smith^

8 3 CS Brown^

2 4 CS Smith^

2 5 CS Brown^

2 6 CS

Disk Storage STUDENT^ Name^

StudentNumber^ Class

Major Smith^

17 1 CS Brown^

8 2 CS Smith^

8 3 CS Brown^

2 4 CS Smith^

2 5 CS Brown^

2 6 CS

…Accessing a Database

2. Using DBMS Software •^ DBMS Software

is a^ collection of general purpose programs

that

enables users to create and maintain an

integrated file database

-^ Separates the job of

data maintenance

from

end-user use of stored data

-^ Available as a packaged software, called

General Purpose Database

Management System (DBMS) • DBMS Main Features^ –^ Data Structural Independence

-^ Different

end-user applications can access database

on disk through DBMS

-^ DBMS makes the applications unaffected

with any structural change happened

in database• DBMS uses control information data (

Data Dictionary

) to inform the

application programs about the structural details of the database files• Data Dictionary is updated automatically

by DBMS in case of any

structural

change

done on the database

Chapter 11 (p268)

.. 2. Using DBMS Software

-^ .. DBMS Main Features^ – Data Query Language - DBMS

lets its users/ application programs to access database

by making use of some query language • A query language is a set of standardized commands

to

perform different database maintenance activities• SQL (Structured Query Language) is the most widely used. • Examples of SQL commands

are

• CREATE TABLE
• to create new data tables (files)
  • SELECT
  • to display selected data records
    • UPDATE
    • to modify selected data records
      • … and many others.

Chapter 11 (p295)

Details of DBMS Components • Database Engine^ – Controls all the data management activities (likedatabase creation, retrieval, validation, manipulationetc.) • DBMS Interface Objects^ – Easy to use graphical interfaces (menus, buttons,wizards etc.) to access the underlying database– Each of these objects are interacting with

database

engine in the background

through

SQL commands

DBMS Package^ Programming Interface

A Working DBMS

STUDENT^ Name^

StudentNumber^ Class^

Major Smith^17

1 CS Brown^8

2 CS GRADE_REPORT^ StudentID^

CourseCode^ SectionCode^

Grade 17 MATH^

1 B 17 CS^

1 C 8 MATH^

2 A 8 CS^

1 A 8 CS^

1 B 8 CS^

1 A

Disk Storage

Integrated FileDatabase

InterfaceObjects

End User

DatabaseApplication

Programmers Database User/Operator

S Q L C O M M A N D S

Database Engine^ Data DefinitionSubsystem^ Database Creation^ Subsystem^ Database Security^ Subsystem

Database Personnel

-^ End Users^ –

Requires access to the database for their jobs– Perform querying, updating and reporting on the stored database– Usually provided with a user friendly application program interface

-^ Database Designers^ –

Identifying the logical/ structural database picture for an environment

-^ Database Administrators^ –

Controlling security, structural updates and performance issues for acorporate database

-^ System Analysts and Application Programmers^ –

Responsible for generating easy to use application programs for the enduser requirements

Chapter 11 (p276)