DATABASE MANAGEMENT SYSTEM - [ INTRODUCTION ]

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 Database 

 Is a Data structure that store organized information in a computer System, easily Managed and Update.
            
            Ex :- A Librarian 

Database Management System 

Create Maintain the DB , provides Controlled Access to DB is a Software that enables user to define, create maintain & control access to the app

        Ex:- MySQL | MS SQL | Oracle 

 Database Application

Computer program that interacts with DB by issuing a request to the DBMS .


                        DB system =  Database +  DBMS + DB  Application 


TYPES OF DBMS 

                    Relational Database 
                    Network Database
                    Object - Oriented Database
                    Hierarchical Database 

3 phases of Data Base Design

                                                            


Conceptual – construct model of the data used in a firm, independent of all physical Considerations.

Logical - in a firm, based on specific data organization, independent of database Management System

Physical – create base relations, file organizations and indexes

 

Essential concepts of ER modeling


Entity Types / Attribute/ relationship Types

Entity Types - weak and Strong

Strong Entity Types – ET that is not existence - depend on some other ET

Weak Entity Types – ET that is existence - depend on some other ET.

 

Attribute – property of an entity or a relationship type.

Attribute Domain – set of allowed values for one or more attribute.


Different Type of Attribute

Simple Attribute - care atomic values, which cannot be divided future.

Composite Attribute – Multiple components – care made of than one simple attribute.

                                    


Single – valued Attribute:-  An Attribute that has any single value for each occurrence of an entity type.


                                                                Ex:- Age , Name, Gender 

Multi – valued Attribute: - An attribute that has more than one value for an occurrence of   type.



                                                                Ex: - Mob_no, Email_id

Derived – Attribute – which can be derived from another attribute. Here  attribute “Age” is a derived attribute as it can be derived from the attribute “DOB”.



                                                                Ex :- Age

Key Attribute – which can identify an entry uniquely in an entity.  Here, the attribute “Roll_no” is a key attribute as it can identify any student uniquely.

Relationship Types   - Set of Meaning full associations among entity types.


Degree of Relationship

 number  of participating entities in relationship.

 

Unary Relationship 


One Person is married to only person 

 

Binary



It is one of the most common types of relationship which requires two entities in a relationship.

                    Ex - Teacher is enrolled in a subject.


 Ternary


Three entities sets in a relationship are ternary relationships. For example, the relationship among Doctor, patient  and Medicine  

 

Binary Relationship Can be  3 ways

  •  One to one
  •  One to many
  •  Many to many

 

Structural Constraints

Main type of constraints on relationship is called “Multiplicity”

                Multiplicity = Cardinality + Participation  

 



Participation - all or one some entity occupancies participate in Relationship 

Cardinality  -Describe mac on of possible relationship occurrences for an entity participating in given relationship type.(almost  values, maximum, possible occurrences)


0 - not must be Participate

1 - must be Participate  

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