Wednesday, 23 December 2015

Codd Rules:IBPS IT Officer Exam Notes

Codd Rules:IBPS IT Officer Exam Notes

Codd Rules-IBPS IT Officer Study Material Professional Knowledge Exam notes: Bank Exam is the most dreamed posts for candidates from different educational back ground these days. Especially engineering graduates prefer to grab the opportunity as IT Officer in the bank. IBPS Specialist Officer Exam notification is announced recently in hunt of best candidates in various specialized field in all the 22 participating banks. IBPS IT Officer is one among it and engineering graduates are preparing for the exams hoping for the best.

In our extensive search of IBPS Specialist Officer previous papers we found that data schemes material is very important for aspirants in exam. So here we prepared Data Schemes material for all the aspirants. So candidates are advised to make use of the material as it will help the candidate to score high.
Along with this material we are trying to cover every important concept in DBMS as it is the most the part where most of the questions appear in the exam.  Hopefuls preparing for IBPS IT Officer Exam can download all these materials and prepare with it. For more materials we advise the job seeker to stay connected to our page regularly in the quest of knowledge to crack the exam.

Data Schemes:

 
The diagrammatic representation of the structure of data is known as Data Scheme, which represents the set of data that is being captured, manipulated, stored, retrieved, transmitted, or displayed. It can be a complex diagram with all kinds of figures that illustrates the data structure and the relationships to one another in a relational database in the data warehouse.

It is important to differentiate between the description of the database and the database itself. And that description of the database is called as database scheme or also known as metadata.
The content of the database and the data may change with the time. The database state at a particular time defined through the currently existing content, their attributes and the relationship is called as database instance.

The database designing is differentiated between two levels of abstraction and their respective data schemes. They are the conceptual and the logical data scheme.

Conceptual Data Scheme:

The system independent data description is called as conceptual data scheme which means that it is independent from the database or computer systems used.

Logical Data Scheme:

The scheme which describes the data in a data definition language DDL of a specific database management system is known as logical data scheme.
This can be illustrated diagrammatically as follows:

Data Independence:

Data Independence means that the data architecture at each higher level will not be affected by the changes of the next lower level of the architecture.
Even though if there are some changes in storage space or type of some data, for optimization or reorganization, there will be no change in the logical scheme.
There are two levels of data independence. They are:

Physical Data Independence: The ability to change the physical data without causing any changes in the schema or logical data is physical data independence. This can be achieved with the presence of internal level of database and also by transforming from conceptual level to the internal level of the database.

A change is required in between conceptual or internal level, if there is any change in file organization or in the physical device


Logical Data Independence: The ability to change the conceptual schema without affecting the existing external schemas is logical data independence. It also insulates application programs from operations like splitting of a record into two or more records or combining two records into a single record.

To achieve logical data independence is difficult when compared to physical data independence because it requires database flexibility and also the programmer should predict the modifications and future requirements in the design.

CODD’s Rules:

Codd proposed a set of thirteen rules which defines the requirements of a database management system to be considered as a relational database management system.
These are a set of thirteen rules numbered from 0 to 12. They are:

Rule 0: The Foundation Rule
An RDBMS must use its relational capabilities to manage the data which is stored. And the system must qualify as relational, as a database and also as a management system.

Rule 1: The Information Rule
This rule states that all the information which is stored in database must be a stored in table formats.

Rule 2: The Guaranteed Rule
In this rule, it states that every data element must be accessible logically with its table-name, attribute-name and the primary key.

Rule 3: Systematic Treatment Of Null Values
This rule states that the NULL value must be given a systematic treatment like giving its details such as data is not applicable or data is missing etc.

Rule 4: Active Online Catalog
In this rule, it states that the structure of whole database should be stored in an online catalog like data dictionary. And this can be accessible by the authorized users.

Rule 5: Comprehensive Data Sub-Language Rule
This rule states that the system should support any relational language that has a linear syntax, that can be used within application programs and interactively. And also that supports data manipulation operations, data definition operations, integrity constraints, transaction management operations and security.
Rule 6: The View Updating Rule
In this rule, all views of the database which are updated theoretically must also be updatable by the system.

Rule 7: High-Level Insert, Update and Delete Rule
This rule states that the database should support not only high-level insertion, updation and deletion but also union, intersection and minus operations to get sets of data records.

Rule 8: Physical Data Independence
This rule states that the changes at physical level should not affect the application.

Rule 9: Logical Data Independence
This rule states that the changes at logical level should not affect the application.

Rule 10: Integrity Independence
In this rule, it states that the database must be independent of the application which is using, which means that all the integrity constraints should be independently modified without affecting the application.
Rule 11: Distribution Independence
This rule states that the data distribution locations should not be visible to the users and they must be visible like it is from one site only.

Rule 12: Non-Subversion Rule
In this rule, it says that if a system is providing a low-level interface, then that interface should not be used to subvert the system and bypass security and integrity constraints.

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