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Data Bases

History

Definition

Main Components of a DataBase

Conclusion

Mohamed Ennahdi El Idrissi



2

History

The earliest know n use of the term 'd ata base' w as in June 1963, whenthe System Development Corporation sponsored a symposium1

under the title Development an d Management of a

Computer-Centere d Data Base

The f irst database management systems w ere developed in the 1960s.

1-Symposium

: meeting o

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for th

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3

Def inition

The term database originated w ithin the computer industry.

A possible def inition is that a database is a collection of records storedin a computer in a systematic w ay, so that a computer program canconsult it to ans w er questions. The items retrieved in ans w er to queriesbecome information that can be used to make decisions.

Another possibile def inition is that it is a collection of data arrangedfor ease and speed of search and retrieval. Also called d ata bank.

The computer program used to manage and query a database is know nas a data base management system (DBMS).

The properties and design of database systems are included in thestudy of information science.



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Main Components of a Data Base

DataBase

R ecor d s Schemas DataBase Mod els

RecordsetObjects Description Theories of a

DataBase use &

Structure

Structure and Use

Description

Table

Items

Net work Model

DBMS

Hierarchical Model Relation Model Object Model

(Data Base Management System )



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RECORDS



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Records

The central concept of a database is a collection of records, or piecesof know ledge.

A record represents a single, implicitly structured data item in a table.

A recor

dset is a data structure that consists of a group of recor

ds, andcan either come f rom a table or as the result of a query to the table.

A table can be thoug ht of as consisting of rows and columns or fiel d s .Each row in a table represents a set of related data, and every row inthe table has the same structure.

An other def inition of a table: it is a set of data elements (values ) thatis organized using a model of horizontal row s and vertical columns.



7

SCHEM A



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Schema

Typically, for a given database, there is a structural description of the

type of f acts held in that database: this description is know n as a

schema.

The schema d escribes the objects that are represented in the database, and

the relationships among them.

There are a number of diff erent w ays of organizing a schema, that is,

of mod eling the d atabase structure : these are know n as database models ( ordata models ).



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D A T AB ASE MODELS



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DataBase Models

A database model is a theory or specif ication describing how adatabase is structured and used.

There are many types of database models:

o Hierarchical Mod el

o Network Mod el

o R elational Mod el

o Object Mod el



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Hierarchical Mod el

Data in a hierarchical model is organized into a tree-like structure



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Network Mod el

The network model allow s each record to have multiple parent and child

records, forming a lattice structure.

Lattice

Structure



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R elational Mod el

In the relational model data are stored in tables linked w ith each other by primary

and/or foreign keys including the possibility of using relational algebra operations inqueries.



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Object Mod el

TheObject model allow s three concepts:Data abstraction -- Encapsulation -- Inheritance. Tables are linked bet w een each other by ref ererences (REF )



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Bibliography

www.wikipedia.com

www.answers.com

www.wordreference.com

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