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8/6/2019 English Presentation Databases
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Data Bases
History
Definition
Main Components of a DataBase
Conclusion
Mohamed Ennahdi El Idrissi
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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
r co
nf erence
for th
e public discussio
nof
so
me to
pic especially o
ne in wh
ich
th
e participantsform an audience and make presentations
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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.
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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