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Database ManagementDatabase Management

(Basic Concepts)(Basic Concepts)

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What is Data-items/Fields?

A data-item is a single fact about something that

interests us.

A fact can be any characteristic of an object.

Salesperson

Number

Salesperson

Name City State

Office

Number

Commission

Percentage

Year of

Hire

137 Siddharth Hyd AP 1284 10 1995

Figure 2.1 Facts about salesperson Siddarth.

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Attributes

Attribute - a property of, a characteristic of, or a factthat we know about an entity.

Some attributes have unique values within an entityset.

SalespersonNumber

SalespersonName City State

OfficeNumber

CommissionPercentage

Year ofHire

119 Taylor New York NY 1211 15 2003

137 Baker Detroit MI 1284 10 1995

186 Adams Dallas TX 1253 15 2001

204 Dickens Dallas TX 1209 10 1998

255 Lincoln Atlanta GA 1268 20 2003

361 Carlyle Detroit MI 1227 20 2001

420 Green Tucson AZ 1263 10 1993

Figure 2.2 Salesperson file.

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Records and Files

Records /Tuples- each row of a structure like above

Fields/Attributes - the columns, representing the facts

File - the entire structure

SalespersonNumber

Salesperson Name City State

OfficeNumber

CommissionPercentage

Year ofHire

119 Taylor New York NY 1211 15 2003137 Baker Detroit MI 1284 10 1995

186 Adams Dallas TX 1253 15 2001

204 Dickens Dallas TX 1209 10 1998

255 Lincoln Atlanta GA 1268 20 2003

361 Carlyle Detroit MI 1227 20 2001

420 Green Tucson AZ 1263 10 1993

Figure 2.2 Salesperson file.

key

field

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Records and Files

Record type - a structural description of each and everyrecord in the file

Record occurrence / Record instance - a specificrecord of the salesperson file

Salesperson

Number

Salesperson

Name City State

Office

Number

Commission

Percentage

Year of

Hire

119 Taylor New York NY 1211 15 2003

137 Baker Detroit MI 1284 10 1995

186 Adams Dallas TX 1253 15 2001

204 Dickens Dallas TX 1209 10 1998

255 Lincoln Atlanta GA 1268 20 2003

361 Carlyle Detroit MI 1227 20 2001

420 Green Tucson AZ 1263 10 1993

Figure 2.2 Salesperson file.

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What is a DBMS?

A DBMS is a combination of hardware and software

that can be used to set up and monitor a database, and

can manage the updating and retrieval of databasethat has been stored in it.

What is a database ?

A database is a collection of related information

stored so that it is available to many users for

different purposes

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DBMS as an interface betweenDBMS as an interface between

physical database and Users Requestsphysical database and Users Requests

Queries

COBOL/C

DBMS OperatingSystem

Database

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DBMS facilitiesDBMS facilities Creating a file, addition to data, deletion of data, modification of data;

creation, addition and deletion of entire files

Retrieving data collectively or selectively

The data stored can be stored or indexed at the users discretion anddirection

Various reports can be produced from the system. These may be eitherstandardized report or that may be specifically generated according to

specific user definition.

Mathematical functions can be performed and the data stored in thedatabase can be manipulated with these functions to perform the desiredcalculations

To maintain data integrity and database use

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Advantages of DBMS

1. Reduction of Redundancies

2. Sharing Data

3. Data Integrity

4. Data Security

5. Conflict Resolution

6. Data Independence

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Disadvantages of DBMS

Cost

Backup and recovery operations are fairlycomplex in a DBMS environment

Centralization of data increases the potentialseverity of security breaches and disruption

due to downtimes and failures