Question Bank — Database Concepts

QUESTION BANK

CBSE Class 12 Computer Science – Chapter 8: Database Concepts
(Strictly based on NCERT textbook content and terminology)

Section A — MCQs (1 mark each)

1. Which of the following is a limitation of the file system that arises because the same data are duplicated in different files?
(a) Data isolation (b) Data redundancy (c) Data dependence (d) Controlled data sharing

2. In the relational data model, the number of attributes in a relation is called its:
(a) Cardinality (b) Degree (c) Domain (d) Tuple

3. A special value used in a relation to represent unknown or non-applicable data for an attribute is:
(a) Zero (b) Empty (c) NULL (d) Blank

4. Which key is used to establish a relationship between two relations?
(a) Candidate key (b) Primary key (c) Foreign key (d) Alternate key

5. The snapshot of a database at any given point of time is called:
(a) Database schema (b) Database instance (c) Meta-data (d) Data dictionary

6. In the STUDENTATTENDANCE database, which attribute(s) form the composite primary key of the ATTENDANCE relation?
(a) RollNumber (b) AttendanceDate (c) {RollNumber, AttendanceDate} (d) GUID

7. Which of the following is not a property of a relation?
(a) Each attribute has a unique name (b) Sequence of tuples is significant (c) All values in an attribute belong to the same domain (d) Each tuple is distinct

8. Meta-data in a DBMS is also known as:
(a) Database engine (b) Data dictionary (c) Query (d) Foreign key

9. Assertion (A): GUID is a candidate key in the GUARDIAN relation.
Reason (R): No two guardians have the same GUID and it can uniquely identify each tuple.
Choose the correct option:
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

10. Assertion (A): Data inconsistency can occur in a file system when the same data are maintained in multiple files.
Reason (R): Different users maintain separate files without any link or mapping between them.
Choose the correct option:
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.

Section B — Very Short Answer (2 marks each)

1. Define the term database schema. Give one example from the STUDENTATTENDANCE database.

2. Differentiate between degree and cardinality of a relation with reference to the GUARDIAN relation.

3. What is a candidate key? Name the candidate keys of the GUARDIAN relation.

4. State any two limitations of the file system that are overcome by a DBMS.

5. What is meant by data constraint? Give one example from the chapter.

6. Define foreign key with reference to the STUDENT and GUARDIAN relations.

Section C — Short Answer (3 marks each)

1. Explain how a DBMS reduces data redundancy by splitting the original STUDENT file into STUDENT and GUARDIAN relations. Support your answer with the school example.

2. Consider the following relation structure (as given in the chapter):
GUARDIAN(GUID, GName, GPhone, GAddress)
Identify the primary key and alternate key. Justify why phone number alone may not be suitable as a permanent primary key.

3. With reference to the three relations STUDENT, GUARDIAN and ATTENDANCE, explain the concept of data mapping and why it is not supported in a file system.

4. Consider the following table fragment (ATTENDANCE relation):
AttendanceDate | RollNumber | AttendanceStatus 2018-09-01 | 1 | P 2018-09-01 | 3 | A
If a student’s name spelling is changed in the STUDENT relation, what problem arises in the file system that is avoided in the DBMS? Explain using the concept of data inconsistency.

5. State any three properties of a relation as mentioned in the NCERT chapter. Explain any one property with an example from the GUARDIAN relation.

Section D — Long Answer (5 marks each)

1. Design a simple relational database for a school library to store data about books and members. Clearly show:
- Relation names with attributes
- Primary key(s) and foreign key(s)
- How redundancy of member details can be avoided
Use NCERT terminology (schema, primary key, foreign key, etc.).

2. Consider the STUDENT, GUARDIAN and ATTENDANCE relations given in the chapter. Perform the following operations one by one and show the state of the relevant tables after each operation using a trace table:
(a) Insert a new student (RollNumber = 7, SName = “Rivaan”, SDateofBirth = “2003-01-10”, GUID = 111111111111)
(b) Update GPhone of GUID 444444444444 to 9812345678
(c) Delete the record of RollNumber 3 from ATTENDANCE for date 2018-09-01
Explain each step with reference to insertion, update and deletion operations.

3. “File system suffers from data dependence.” Explain this statement with the help of an example from the chapter. How does a DBMS overcome this problem?

Section E — Case/Source-Based (4 marks each)

Case 1: School Canteen Database

A school canteen wants to maintain records of items and generate bills. It decides to use a DBMS instead of separate files for items and sales.

Sub-questions:

(a) Identify two limitations of the file system that the canteen would face if it continues with manual files.
(b) Suggest two relations (tables) with suitable attributes. Mark primary key(s) and foreign key(s).
(c) Which column(s) can have the NOT NULL constraint? Why?
(d) How will the DBMS ensure that a bill is generated only for items that exist in the canteen?

Case 2: Banking Application

A bank maintains customer information, account details and transaction records in a database.

Sub-questions:

(a) Name the relations that can be created and list at least three attributes for each.
(b) Identify a possible composite primary key and justify.
(c) Which attribute can act as a foreign key between the Account and Transaction relations?
(d) Explain how controlled data sharing can be implemented so that customers can only view their own account details.