A complete note of Database Management System(DBMS)/RDBMS/Database management system notes class 12 nepal 2078

 

1. Short answer questions

a) What id a database ? List the major uses of database application software ?

👉️ A database is a collection of related information about a subject organized in a useful manner that provides a base or foundation of the procedure such as retrieving information , concluding amd make a decision.

A database is a collection of interrelated data of a certain place or person or things in such a way that it can be easily accessed in such an application program like DBMS.

Major uses of database application software are as follows:-
- Storing data
- Accessing data when it is required
- Updating / Modifying data
- Deleting or removing data
- Maintaining accuracy of the data
- Reducing data redudancy
- Providing timely and accurate information
- Providing security on the data.

b) Define database management system ( DBMS ). List out the objectives of Database management system (DBMS)?

👉️A database management system is a collection of program that a user to create and maintain a database.

The objectives of database management system (DBMS) are :-
1. To provides a storage area for the mass amount of relevant data.
2. To provide prompt response to the user request for data.
3. To make access to the data easy for the end-user.
4. To eliminate data redundancy ( duplication of data ).
5. To allow multiple users to be active at one time.
6. To allow the growth of the database.
7. To protect the data from the physical harm and unauthorized access.

c) Give two advantages of using a database rather than a number of separate files .

👉️Any two advantages of using a database rather than a number of separate files are as below:-
1. Data cannot be duplicated.
2. Data can be shared and security.
3. Integrity can be maintained very well.
4. It is very easy to search for data.
5. It is easy to work.

d) What is an E-R diagram ? Explain the advantages of the E-R diagram in system design.

👉️ An E-R diagram is a graphical representation pf different entities and theri relationship . It is a graphical representation of the database. The overall logical structure of a database can be expressed graphically by an E-R diagram.

The advantages of the E-R diagram in system design are as follows:-
1. It is simple and easier to understand.
2. It supports physical database creation.
3. It provides a higher level description of the system.
4. It can be generalized or specialized based on needs.
5. It is highly flexible to use as additional relationships can be added as per need.
6. It provides a visual representation of the database design.
7. It allows designers to effectively communicate the features of the database.

e) What is normalization ? Explain first normal form (1NF ) , second normal form (2NF ), third normal form (3 NF).

👉️The process of decomposing a big table into much dmaller and simplest table is called normalization.
Normalization works through a series of stage called normal form. There are most important and widely used normal forms are:-
1. First Normal Form (1NF )
2. Second Normal Form (2NF )
3. Third Normal Form ( 3NF )
4. Boyce Codd Normal Form ( BCNF )
5. Fourth Normal Form ( 4 NF )

✏️First normalization form :- A relation or table is said to be in 1NF if its all attribute are atomic. Thai is , there should not be any repeating groups of an attribute . The purpose of 1NF is to elimate repeating groups of attribute in an entity.

✏️Second normalization form :- A relation is said to be in second normal form if it is in first normal form and each attribute is functionally dependent on the entire primary key. The purpose of the second normal form is to eliminate partial key dependences.

✏️Third normalization form:- A relationship is said to be in the third normal form if it is in the second normal form and it does not contain any transitive dependency on the primary key.

f) Explain the benefits of a centralized Database ?
👉️The benefits or advantages of centralized Database are:-
1. It is simple to implement and manage.
2. It has less or no risk of data loss.
3. It has a low cost of implementation and operation.
4. It is suitable for a small organization with limited data and users.
5. High security can be provided.

g) What is data security ? How it can be implemented?
👉️ The protection of data or destruction from the unauthorized access, alternation or destruction of data is called data security. Data security is the means of ensuring that data is kept safe from corruption and that access to it is suitably controlled .
Data security can be implemented are as follows
1. The place or the site containing the computer systems must be physically secure against external intruders.Software security is not enough for the security of a system , physical security is a must.
2. User must be authorized carefully to reduce the change of such user giving access to an intruder.
3. The database system is highly secured weakness in the operation system may provide the pathway of unauthorized access.
4. Security should also be provided by the database system itself, som database user may be authorized to access only a limited portion of database.

h) State and describe different types of data integrity .
👉️ Data integrity or integrity constraint is a rule that restricts the value that may be present in the database. Integrity constraints ensure that change made to the database be authorized user do not results in a loss of data consistency.

The different types of data integrity are:-
1.Entity integrity :- Entity integrity is the rule that no column that is part of the primary key may accept null values.

2. Referential integrity :- The referential integrity rule states that if table A contains a foreign key that matches the primary key B then values of this foreign key either must matche the value of the primary key of some row in table B or must be null.

i) What is database ? List out the advantages of a Database Management System .
👉️ A database is a collection of interrelated data of a certain place or person ot things in such a way that it can be easily accessed by an application program like DBMS.

The advantages of a Database Management System are:-
1.Data can be shared( Concurrent access of data ).
2. Reduce data redundancy.
3. Integrity can be maintained.
4. Data independence.
5. Data availability.
6. Standard can be enforced.
7. Security can be improved.
8. Inconsistency can be avoided.
9. Providing multiple user interfaces.
10. Providing backup and recovery.

j) Define the term " SQL" and Data " security".
👉️ SQL ( Structured Query Language ):- SQL is the relational language for the end- user. It contains the statements that describe the data contained in the database. SQL is used as an intermediary and a standard in accessing a large number of different types of database system. There are many types of SQL the most commonly used types are two; one to specify the database schema and the other to express database queries and update .

Data security :- The protection of data against unauthorized access is called security . The means of ensuring that data is kept safe from corruption and that access to it is suitably controlled . Thus data security helps to ensure privacy . It helps to protecting the personal data. Data security is to ensure the Data theft, Data privacy, Data corruption etc of the database.

2. Long answer questions .

a. Explain the different models used in the database?

👉️The different models describe the structure of a database. It is a collection os conceptual tools for describing data , relationship etc. It defines how the data are stored and accessed.

There are three types of database Models used in the database. They are;

✏️ Hierarchical Database Models :- In a hierarchical database model , records are logically organized into a hierarchy of relationship . A hierarchically structured database is arranged logically in an inverted tree pattern. A records in the hierarchy are called nodes. Each node is related to the other in a parent-child relationship . Each node is related to the other in a parent-child relationship . Each parent record may have one or more child record in the hierarchy is called the root record.

Some advantages of hierarchical Database Models are:-
1. Searching is fast and easy if the parent is known.
2. It is very efficient in handling " One to Many" relationship .
3. It helps to build complex systems from simple components.

Some disadvantage of hierarchical Database Models are:-
1. It can't handle " Many to Many" relationship.
2. It increases data redundancy.

✏️Network Database Model:- Network database model is a modified verson of the hierarchical database. In network database structure each node may have several parents. A network database model views all records in sets.

Advantages of Networks Database Model are:-
1. It is more fiexible than hierarchical model because it accepts " Many-to-Many" relationship.
2. It reduces reducancy because data should not repeated if same data is needed.
3. Searching is fast of multi directional pointers.

Disadvantages of Network Database are:-
1. It is one of the complex database models.
2. It needs larger programs to handle the relationships.
3. It is less secure compared to the hierarchical .
4. Pointer is needed to increase the overhead of storage.

✏️ Relational Database Model In relational database model data are arranged in two dimensional table which is easy for a user to develop and understand . This type of model can also be described mathematically. Because many managers often work with tabular form data, it is easy for most of them to understand the structure used in a relational database

Advantages of Relational Database Model are:-
1. It is very low data redundancy.
2. Normalization of yhe database is possible.
3. Rapid processing of database is possible.

Disadvantages of Relational Database Models:-
1. It is more complex then other models.
2. Too many rules make database non-user friendly.

b) Define the term Relational Database Model System ( RDBMS ). Explain the centralized and decentralized database models?

👉️The software used to store , manage , query and retrieve data stored in a relational database is called a relational database management system ( RDBMS ).
The RDBMS provides an interface between user and applications and the database as well as administratI've for managing data storage, access and performance.

Centralized database models :- Centralized database system are those system that run on a single computer system. A computer system may be a single user pr multi user . A database system designed for a single user system does not provides many of the facilities that a multiuser database system provides.

Advantages of centralized database models are as below:-
1. It is simple to implement and manage.
2. It has less or no risk of data loss.
3. It has a low cost of implementation and operation.
4. It is suitable for a small organization with limited data and user.
5 High security can be provided.

Disadvantages of centralized database models :-
1. Faliure of the server will completely down the whole computer system.
2. It is not reliable as a distributed database.
3. It is not appropriate for big organizations , which have a large number of users and computers.

Decentralized database models/ Distributed database models:- In decentralized database models the database is stored on several computers. Decentralized database are database located at different places. They facilitate easy access to data from any location. It has the problem of control of security , increased the problems of control of the database and needs more computer resources .

Advantages of Decentralized database models are :-
1. Faliure of a site does not affect the whole computer system.
2. It is much as compared to the centralized database system.
3. The performance and service are better than centralized database system.

Disadvantages of decentralized database are:-
1. It is complex to implement and manage.
2. It has a high risk of data theft , hacking etc.
3. It has a high cost of implementation and operation.

A complete note of Database Management System(DBMS)/ Rdbms 2078 Nepal/Database management system/RDBMS/Database management system computer science notes nepal 2078/computer science notes class 12 nepal 

A complete note of Database Management System(DBMS)/ Rdbms