NEB Grade 12 Computer Science Important Question with Solution-Database Management System

Database Management System

     i. Define database and DBMS. Explain the advantages of a database system over a flat-file system.

Ans: A database is a collection of data that is organized in a specific way, allowing for efficient retrieval and manipulation of the data. A DBMS (Database Management System) is software that manages and controls access to the database.

Advantages of a database system over a flat-file system include:

1. Data integrity: A database system enforces data constraints and relationships, ensuring that the data is accurate and consistent.
2. Data independence: A database system allows for changes to be made to the structure of the data without affecting the applications that use the data.
3. Concurrent access: A database system allows multiple users to access the same data simultaneously, without interfering with each other.
4. Data security: A database system provides various security mechanisms to control access to the data and prevent unauthorized access.
5. Data sharing: A database system allows for data to be easily shared among different applications and users.
6. Data Backup and Recovery: Database system provides various options for data backup and recovery, which makes it easy to recover data in case of any failure.

    ii.      What is normalization? Explain 1NF, 2NF and 3NF.

Ans: Normalization is the process of organizing data in a relational database in such a way as to minimize data redundancy and dependency. It is a technique used to design relational database tables in a way that reduces data duplication and improves data integrity.

There are several normal forms, each building upon the previous one:

1. First Normal Form (1NF): A table is in 1NF if it meets the following criteria:
• Each table cell contains only a single value.
• Each row is unique.
• Each column has a unique name.
2. Second Normal Form (2NF): A table is in 2NF if it meets the following criteria:
• It is in 1NF.
• It has no partial dependencies.
• All non-key columns are dependent on the primary key.
3. Third Normal Form (3NF): A table is in 3NF if it meets the following criteria:
• It is in 2NF.
• It has no transitive dependencies.
• All non-key columns are not dependent on other non-key columns.

In summary, 1NF is about atomic values, 2NF is about non-repeating groups, and 3NF is about non-transitive dependencies.

Normalization helps to improve the efficiency and maintainability of a database by eliminating data redundancy and ensuring data integrity. It helps to minimize the data duplication and increases the performance of the database by reducing the amount of data stored.

  iii. Who is a database administrator? What are the major responsibilities of a Database Administrator?

Ans: A database administrator (DBA) is a professional who is responsible for the overall management, performance, security, and maintenance of an organization's databases. They ensure that the databases are running efficiently, are secure, and can meet the needs of the organization.

The major responsibilities of a Database Administrator include:

1. Installation, configuration, and upgrading of database software.
2. Designing and implementing a database security plan to protect data from unauthorized access.
3. Monitoring and optimizing the performance of the databases, troubleshooting, and resolving issues as they arise.
4. Creating and maintaining backups of the databases, ensuring that data can be recovered in case of an emergency.
5. Managing the storage and capacity of the databases, ensuring that there is enough space for the data and that the data is stored in an efficient manner.
6. Managing the users and roles that have access to the databases, ensuring that they have the appropriate level of access.
7. Creating and maintaining documentation for the databases, including data dictionaries, flowcharts, and other documentation to help others understand the databases.
8. Keeping abreast of new technologies and industry trends to ensure that the databases are running on the latest and most efficient software.

In short, DBAs are the gatekeepers of the organization's data and are responsible for ensuring the data is available, accurate, and secure. They must be able to troubleshoot and solve problems quickly, have a deep understanding of database technology, and be able to work well under pressure.

 iv.            Explain the centralized and decentralized database models.

Ans:

Centralized database model: In a centralized database model, all data is stored in a single location, usually on a central server. This server is responsible for managing and maintaining all data, including data storage, backups, and security.

Decentralized database model: In a decentralized database model, data is distributed across multiple locations, usually in the form of smaller databases. Each location is responsible for managing and maintaining its own data, including data storage, backups, and security.

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 v.            Explain the DDL and DML.

Ans:

DDL (Data Definition Language) is a type of SQL (Structured Query Language) that is used to define the structure and organization of a database. It is used to create, alter, and delete database objects such as tables, views, indexes, and procedures. Some common DDL commands include CREATE, ALTER, and DROP.

DML (Data Manipulation Language) is a type of SQL that is used to manipulate the data stored in a database. It is used to insert, update, and delete data from tables and views. Some common DML commands include SELECT, INSERT, UPDATE, and DELETE.

In summary, DDL is used to define the structure and organization of a database and DML is used to manipulate the data stored in a database. DDL commands are used to create or modify the database structure, while DML commands are used to add, update, or delete data from the database.

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Note: DDL and DML are both part of SQL, the programming language used to interact with relational databases.