Short Note On DBA

Definition of DBA:-
                                     Database administrator(DBA) is a professional Person or group of professional persons responsible for designing and maintaining the database.The role of database administrator is very important for  successfull database execution.
        

Rolls Of DBA :
                         Some of the major roles of DBA of an organisation listed below:-

1.Designing schemas :-
                                          DBA designs the structure of complete database .The collection of       schemas is decided by the DBA with the help of conceptual database definition.


2. Designing constants on database items:-
                                                                       DBA designs the constant or rules of the data-items (attributes)  which properly defined in the data dictionary of database manager. This contents ensure the integrity of the database, this keep the database in conscious state.

3.Modification to the physical schema structure:-
                                                                                    DBA is entitled to modify the physical structure  when it is required or when some changes are made to the database.The modification is done using DDL commands are statements.

4.Authorisation of grants:-
                                              The biggest goal of DBA is to decide what part of the database is accessed by whome. A user can only read the data and read or write the data or modify the data structure itself are few types of accesses, this kind of grant is  the functionality of the DBA or decided by DBA.

5.Imposition of security:-
                                             DBA has to control the data form unauthorised accesses, To improve the security of the data  stored in the database Is decided by the DBA.In future routine maintenance is also done by the DBA In the case of some Special purpose.

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short note on normalization of database with examples

Definition of Normalization :
                                                                   Database Normalization is a technique of organising data in the database.Normalization is a  systematic approach of decomposing tables to element data redundancy and undesirable characteristics like insertion, updation,and deletion  anomalies.

 Why Normalization is required ?? 

  The main objectives of Normalization are :- 

                 # To eliminate redundant data.
                 # To free the collection of relations from insertion,updation and deletion anomalies.             
                 # To make the relation model more informative to the users.

Redundant data anomaly :-
                                                            The database to be designed may suffer from duplication of data.To fulfill the capability of relational database ,it may be required to repeat the values of the data in the    database. This resulted in Redundant data anomaly.
      Example:

       


Insertion anomaly :-
                                                The problem of inserting a new tuple into the database without the value of the all attributes  Is called insertion anomaly.If new attribute values are to be added to the database,then it can only be done when the values of other attributes of the tuple are available.
        
  Example:

              -Here in relation T1  we cannot insert the subject code of mathematics MTMH unless at least one student enroll for that subject.


Deletion anomaly :-
                                                 The problem of losing important data of the database by deleting a tuple from the database is called Deletion anomaly.If an tuple is to be deleted,a complete row from the relation is deleted resulting in loss of important data.

 For Example :
                        Consider a relation T1 is consist of the details of a college students.Suppose there is a single student in geography department who withdrawas his enrollment hence his full record or tuple must be deleted.
        Along with it we also lose the Information that the subject code of Geography is GEOH.

Updation anomaly :-
                    When duplicate data is reflected in many rows ,any changes to one attribute value ,then it must replaced in all  the other touple otherwise the database will lose it's integrity resulting in updation anomaly.

 For  Example :
                      Consider the same relation T1,if it is decided to change the subject code of computer science form CMSH to CMS Then this must be changed thoughtout the database otherwise it may be lead to updation anomaly.

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