Database management system



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DBMS: is a software which provides environment to store and retrieve the data from data base.

Data: Data is a raw fact

Data base: is a storing of data with different enterprises


Basically there are 2 type of data

i) Unstructured

ii) Structured: Support relational model data i.e table formated


Components of data base:

1) UI (User interface): Interface between user and application.

DBA          SYSTEM DEVELOPER     END USER


CASE TOOL <----------->   UI------------APPLICATION                                                                    PROGRAM


REPOSITRY -------------DBMS<-------->DATABASE


Advantage and disadvantage of data base

• Retendency: Removing the duplication of data

• Data Security: Only the authenticated user can access the data

• Reduce the application development time

• Conflict resolution and concurrent access

• Crash recovery


Disadvantages


• Expetision is required: the person who know the command can only access the data. i.e technical person is required to access the data


File system vs DBMS

• File system stores the collection of data 

• Retriving of data not easy 

• File system stores some copy of data multiple time

• It take more time

• File system does not having a security


DBMS

• In DBMS we cannot restore the same data, we linked the data 

• Retriving of data is easy 

• Multiple user access the database at a time 

• We can easily recover the data by recovery manager

•DBMS is secure , easy to access and recover


Data model : In which format we are storing the data is called data model 

3 types of data model 

1) Object base data model 

2) Record base data model

3) Physical base data model


1) object base data model: are 2 types

i) Object (Oops) like c++, java 

ii) E-R model : Entity Relationship


E-R model is graphical representation of data

•Entity: real world object representation: Rectangle shape

•Relation: Diamond shape 

•Attributes: Ellipse shape

•Link: shape(-----)


* Table is aslo called as relation 

Row is also called as -- Touple & Record

Column is also called as--- Attribute, Field name, Domain


2)Record : means row 3 types

i) Realtional model:(Table) complete table creating

ii) Network: connection between row to row

iii) Hierchy: It maintain record wise data 

• Structure wise maintain the data like tree 


3) Physical: actual storage of data


• Schema property of table is called schema

Realtion instance data of the table is called relation instance