Class 12 IT 802 Unit 1 : Database Concepts – Basics of RDBMS Question Answer

Unit 1: Database Concepts | Basics of RDBMS

Important Question Answer

1. What is the full form of DBMS?

Answer: Database Management System

2. What is Data?

Answer: Data is a collection of raw facts which have not been processed to reveal useful information.

3. What is Information? Explain with the help of diagram and example.

Answer: The processed data is called Information. Information is produced by data processing.

Data Processing

For example, given the data of the test marks of all the students in a class (data), the average, maximum and minimum marks in the class can be used as indicators of the performance of the class (information).

Example of Data Processing

4. What is Database?

Answer: The collection of related (interrelated) data the haven recorded, organized and made available for searching is called a Database.

5. Write four properties of Database?

Answer: A database has the following properties:-

  • (1) A database is a representation of some aspect of the real world.
  • (2) It is designed, built, and populated with data for a specific purpose.
  • (3) It can be of any size and complexity.
  • (4) It can be maintained manually or it may be computerized.

Unit 1 Database Concepts – NCERT Book Solution

6. What is the need for a Database?

Answer: In traditional file processing, data is stored in the form of files.

A number of application programs are written by programmers to insert, delete, modify and retrieve data from these files.

New application programs will be added to the system as the need arises. But these traditional file systems has some disadvantages. These are-

  1. Data Redundancy: Same information is stored in more than one file. This would result in wastage of space.
  2. Data Inconsistency: If a file is updated then all the files containing similar information must be updated else it would result in inconsistency of data.
  3. Lack of Data Integration: As data files are independent, accessing information out of multiple files becomes very difficult. Database approach overcomes these problems

In database approach, a single repository of data is maintained which is accessed by different users as per their needs.

7. What is DBMS?

Answer: Database Management System (DBMS) is a collection of programs that enables users to create, maintain and use a database. It enables creation of a repository of data that is defined once and then accessed by different users as per their requirements.

8. Write the characteristics of DBMS?

Answer: The main characteristics of a DBMS are: –

  • (a) Self-describing Nature of a Database System: DBMS contains not only the database but also the description of the data that it stores.
  • (b) Insulation Between Programs and Data: Since the definition of data is stored separately in a DBMS, any change in the structure of data would be done in the catalogue and hence programs which access this data need not be modified. This property is called Program-Data Independence.
  • (c) Sharing of Data: A multiuser environment allows multiple users to access the database simultaneously. Thus a DBMS must include concurrency control software to allow simultaneous access of data in the database without any inconsistency problems.

9. What is Data Dictionary?

Answer: Data Dictionary is the repository which stores the Meta-data. It contains the structure of the data and also the constraints that are imposed on the data.

10. What is Meta Data?

Answer: Description of data is called Meta Data i.e. Data about Data is called Meta Data.

11. What is the use of concurrency control software?

Answer: Concurrency control software is allow
simultaneous access of data in the database without any inconsistency problems.

12. How many types of DBMS users? Write their names.

Answer: There are four types of DBMS users.

These are –

  • (a) End Users
  • (b) Database Administrator (DBA)
  • (c) Application Programmers
  • (d) System Analyst

13. Who is the End Users?

Answer: Users who use the database for querying, modifying and generating reports as per their needs. They are not concerned about the working and designing of the database. They simply use the DBMS to get their task done.

14. Who is DBA?

Answer: DBA is the Database Administrator. The DBA administers the database and the DBMS. The DBA is responsible for authoring access, monitoring its use, providing technical support, acquiring software and hardware resources.

15. Who are Application Programmers?

Answer: Application programmers write application programs to interact with the database. These programs are written in high level languages and SQL to interact with the database.

16. Who is System Analyst?

Answer: System analyst determines the requirements of the end users and then develops specifications to meet these requirements.

A system analyst plays a major role in the database design and all the technical, economic and feasibility aspects.

17. What are the advantages of DBMS?

Answer: Advantages of DBMS are:-

  1. Reduction in Redundancy / Reduce Data Redundancy: There is no repetition of the same data.
  2. Improved Consistency: The chances of data inconsistencies in a database are also reduced as there is a single copy of data that is accessed or updated by all the users.
  3. Improved Availability / Sharing of Data: Same information is made available to different users. This helps sharing of information by various users of the database.
  4. Improved Security: Though there is improvement in the availability of information to users, it may also be required to restrict the access to confidential information.
  5. User Friendly: Using a DBMS, it becomes very easy to access, modify and delete data. It reduces the dependency of users on computer specialists to perform various data related operations in a DBMS because of its user friendly interface.

18. What are the disadvantages/limitations of using DBMS approach?

Answer: Two main disadvantages of using a DBMSE are: –

  1. High Cost: The cost of implementing a DBMS system is very high. It is also a very time consuming process.
  2. Security and Recovery Overheads: Unauthorized access to a database can lead to threat to the individual or organization depending on the data stored.

19. Who developed the Relational Database?

Answer: Relational database was developed by E.F Codd at IBM in 1970.

20. What is the Relational Database?

Answer: Relational database is used to organize collection of data as a collection of relations where each relation corresponds to a table of values.

Each row in the table corresponds to a unique instance of data and each column name is used to interpret the meaning of that data in each row.

21. Define the following terms in respect to Relational Database, with the help of example.

(a) Tuple (b) Attribute (c) Relation (d) Domain (e) Degree (f) Cardinality


  • Tuple : A row is called a Tuple.
  • Attribute: A column is called an Attribute.
  • Relation : A table is called as a Relation.
  • Domain: The set of values of an attribute is called Domain. The data type of values in each column is called the Domain.
  • Degree of Relation: The number of attributes in a relation is called the Degree of a relation.
  • Cardinality of Relation: The number of rows in a relation is called the Cardinality of a relation.

22. What is Domain?

Answer: The domain is a set of atomic (or indivisible) values. The domain of a database attribute is the set of all the possible values that attribute may contain.

In order to specify a domain, we specify the data type of that attribute.

Table Creation and Manipulation Question Answer

23. What are the characteristics of Relation?

Answer: Characteristics of Relation are: –

  1. Ordering of tuples is not important in a Relation.
  2. The ordering of attributes is also unimportant.
  3. No two tuples of relation should be identical i.e. given any pair of two tuples, value in at least one column must be different.
  4. The value in each tuple is an atomic value (indivisible).
  5. If the value of an attribute in a tuple is not known or not applicable or not available, a special value called null is used to represent them.

24. What is a Relational DBMS?

Answer: A Relational DBMS (RDBMS) is a DBMS which is based on the relational model. In this DBMS, two or more tables can be interrelated with the help of Primary Key and Foreign Key constraint. This is one of the most commonly used databases.

25. Write the name of five Relational DBMSs?

Answer: Name of five RDBMS (Relational Database Management Systems) are

Oracle, MySQL, IBM DB2, MS Access, OpenOffice Base, Microsoft SQL Server, etc.

26. What is the Constraint in a Relational Data Model?

Answer: Constraints are restrictions on the values, stored in a database based on the requirements.

For example, in the relation EMPLOYEE,

  • the Employee_ID must be a 4-digit number,
  • the Date_of_Birth must be greater than ’31-12-1985′.

27. What is Domain Constraint?

Answer: Domain Constraint specifies that the value of every attribute in each tuple must be
from the domain of that attribute.

28. What is a Key Constraint?

Answer: Constraints like Super Key, Primary Key, Candidate Key, and Foreign Key are known as Key constraints.

29. What is a Super Key?

Answer: Superkey is a set of attributes in a relation, for which no two tuples in a relation state
have the same combination of values.

Every relation must have at least one superkey which is the combination of all attributes in a relation.

For the EMPLOYEE relation, the following are some of the superkeys:

  • (a) {Name, Employee_ID, Gender, Salary, Date_of_birth} – default superkey
  • consisting of all attributes.
  • (b) {Name, Employee_ID, Date_of_Birth}
  • (c) {Employee_ID, Gender, Salary}
  • (d) {Name, Employee_ID, Gender}
  • (e) {Employee_ID}

30. What is a Candidate Key?

Answer: A field/key has the capability to become the primary key, called a candidate key.

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Unit 1 Database Concepts – NCERT Book Solution

Table Creation and Manipulation Question Answer

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