Q1. Define a database. How is it different from a simple file processing system?
Q2. What is data redundancy? Explain how a DBMS helps reduce data redundancy.
Q3. State any two major advantages of using a Database Management System (DBMS) over traditional file systems.
Q4. What do you understand by data inconsistency? Give a brief reason why it occurs in file-based systems.
Q5. Define data sharing and data security in the context of database systems.
Q6. What is metadata? Where is it stored in a DBMS architecture?
Q7. Explain the role of a Database Administrator (DBA).
Q8. What is data independence? Differentiate between logical and physical data independence.
Q9. Give two examples of popular Relational Database Management Systems (RDBMS).
Q10. Explain what is meant by “data integrity” in a database.
Answer Key – Set 1
Ans 1: A database is an organized collection of logically related data structured for easy access, management, and updating. Unlike file systems which store data in isolated files with potential duplication, a database centralizes data management.
Ans 2: Data redundancy is the duplication of the same data in multiple places. DBMS reduces redundancy by centralizing data storage, ensuring each piece of data is stored in only one place.
Ans 3: (i) Reduced data redundancy, (ii) Improved data security and access control.
Ans 4: Data inconsistency occurs when different copies of the same data contain conflicting information, usually caused by updating data in one file while forgetting to update duplicate copies in other files.
Ans 5: Data sharing allows authorized multiple users/applications to access the same database concurrently. Data security ensures that data is protected from unauthorized access or malicious modification.
Ans 6: Metadata is “data about data”—it defines structure, constraints, and schema definitions. It is stored in the database catalog or data dictionary.
Ans 7: A DBA is a professional responsible for authorizing access, coordinating database administration, monitoring performance, and managing backups/recovery.
Ans 8: Data independence is the capacity to change the schema at one level of a database system without having to change the schema at the next higher level. Physical independence protects against changes to internal storage structures, while logical independence protects against changes to conceptual schemas.
Ans 9: MySQL and Oracle (or PostgreSQL, SQL Server).
Ans 10: Data integrity refers to the overall completeness, accuracy, and validity of data stored in a database, enforced using constraints.
Worksheet Set 2: Relational Data Model Terminology
Focus: Tuple, relation, attribute, degree, cardinality, and domain.
COMPUTER SCIENCE / INFORMATICS PRACTICES
Worksheet Set 2: Relational Data Model Terminology
Q1. Define a relation in the context of a relational data model.
Q2. What is a tuple? Give its alternative name in tabular representation.
Q3. Define an attribute and state its alternative name.
Q4. What is meant by the ‘degree’ of a relation?
Q5. Define the ‘cardinality’ of a relation.
Q6. What is the concept of a ‘domain’ in a database table?
Consider a table named Employee containing 5 columns and 12 rows. Answer Q7 and Q8 based on this.
Q7. What is the degree of the Employee table?
Q8. What is the cardinality of the Employee table?
Q9. Explain why rows in a relation do not have a fixed sequential order.
Q10. Can an attribute have values outside its defined domain? Justify.
Answer Key – Set 2
Ans 1: A relation is a table representing a set of data items structured into rows and columns.
Ans 2: A tuple is a single row of a relation, also known as a record.
Ans 3: An attribute is a named column of a relation, also known as a field or column.
Ans 4: The degree of a relation is the total number of attributes (columns) present in the table.
Ans 5: The cardinality of a relation is the total number of tuples (rows) present in the table.
Ans 6: A domain is the pool of all possible atomic values that an attribute can legally accept (e.g., age domain between 0 and 120).
Ans 7: 5 (since degree equals the number of columns).
Ans 8: 12 (since cardinality equals the number of rows).
Ans 9: Relational tables treat rows as mathematical sets where position/ordering carries no semantic meaning; data is retrieved based on query criteria rather than position.
Ans 10: No, attributes must only take values from their respective domains to maintain data integrity.
Worksheet Set 3: Database Keys
Focus: Candidate key, primary key, alternate key, and foreign key.
Q2. What is a primary key? How does it differ from a general candidate key?
Q3. Explain the term ‘alternate key’.
Q4. What is a foreign key? Why is it used in relational databases?
Q5. Can a primary key accept NULL values? Why or why not?
Q6. Consider a table Student with columns RollNo, AdhaarNo, and Email, all of which uniquely identify students. If RollNo is chosen as the primary key, what are AdhaarNo and Email called?
Q7. Can a foreign key accept NULL values? Give a valid scenario.
Q8. What is a composite primary key?
Q9. State the rule of referential integrity.
Q10. Explain why a primary key constraint implicitly enforces both UNIQUE and NOT NULL constraints.
Answer Key – Set 3
Ans 1: A candidate key is a minimal set of attributes that can uniquely identify a tuple within a relation.
Ans 2: A primary key is a designated candidate key chosen by the database designer to uniquely identify records in a table. While all primary keys are candidate keys, not all candidate keys are primary keys.
Ans 3: Candidate keys that are not selected as the primary key are called alternate keys.
Ans 4: A foreign key is an attribute (or set of attributes) in one table that references the primary key of another table, used to establish and enforce a link between data across tables.
Ans 5: No, a primary key cannot accept NULL values because every record must have a valid, unique identifier.
Ans 6: They are called alternate keys.
Ans 7: Yes, a foreign key can accept NULL values unless it is explicitly constrained with NOT NULL (e.g., an employee optional department assignment).
Ans 8: A composite primary key is a primary key formed by combining two or more columns when no single column can uniquely identify records alone.
Ans 9: Referential integrity requires that every foreign key value must match an existing primary key value in the referenced table (or be completely null).
Ans 10: Because uniqueness prevents duplicate identifiers, and non-nullability guarantees every row is identifiable.
Worksheet Set 4: Advantages of SQL & Data Definition Language (DDL) (10 Questions)
Focus: Advantages of SQL and DDL commands (CREATE, ALTER, DROP).
Q1. What does SQL stand for? State its primary purpose.
Q2. State three key advantages of using Structured Query Language (SQL).
Q3. What is Data Definition Language (DDL)? Name any three DDL commands.
Q4. Write an SQL statement to create a database named Hospital.
Q5. Write an SQL statement to create a table Doctor with columns DocID (int, primary key) and DocName (varchar(30), not null).
Q6. Write an ALTER TABLE command to add a new column Specialization of type varchar(25) to the Doctor table.
Q7. Write a command to delete the entire structure of the Doctor table permanently from the database.
Q8. Distinguish between DDL and DML in brief.
Q9. Write a query to drop/delete the database named Hospital.
Q10. What is the purpose of the DESCRIBE command in DDL operations?
Answer Key – Set 4
Ans 1: Structured Query Language. Its primary purpose is to communicate with, query, update, and manage relational databases.
Ans 2: (i) High-level English-like syntax, (ii) Non-procedural nature (specifies what to get, not how to get it), (iii) Universal standardization across RDBMS platforms.
Ans 3: DDL is a subset of SQL used to define and modify database structures and schemas. Commands: CREATE, ALTER, DROP.
Ans 4:
CREATE DATABASE Hospital;
Ans 5:
CREATE TABLE Doctor (DocID INT PRIMARY KEY, DocName VARCHAR(30) NOT NULL);
Ans 6:
ALTER TABLE Doctor ADD Specialization VARCHAR(25);
Ans 7:
DROP TABLE Doctor;
Ans 8: DDL deals with database structures and schemas (tables, databases), whereas DML deals with storing, retrieving, modifying, and deleting data rows within those structures.
Ans 9:
DROP DATABASE Hospital;
Ans 10: The DESCRIBE command displays the schema structure of a table, including column names, data types, and constraints.
Worksheet Set 5: DQL (SELECT) & DML Commands
Focus: Data Query Language (SELECT), Data Manipulation Language (INSERT, UPDATE, DELETE).
Q1. What is Data Query Language (DQL)? Name the principal command associated with it.
Q2. Define Data Manipulation Language (DML) and list three DML commands.
Q3. Write a query to display all records from a table named Employee.
Q4. Write a query to insert a new row into an Employee table with EmpID = 101 and Name = 'Rohan'.
Q5. Write an UPDATE query to change the salary of employee 101 to 60000.
Q6. Write a DELETE query to remove records of employees whose salary is less than 20000.
Q7. Explain the difference between DQL and DML.
Q8. Write a query to display unique departments from an Employee table.
Q9. What happens if you execute an UPDATE statement without a WHERE clause?
Q10. What happens if you execute a DELETE FROM table_name; statement without a WHERE clause?
Answer Key – Set 5
Ans 1: DQL is the subset of SQL used for querying and retrieving data from databases. The primary command is SELECT.
Ans 2: DML is used for managing data within database tables. Commands: INSERT, UPDATE, DELETE.
Ans 3:
SELECT * FROM Employee;
Ans 4:
INSERT INTO Employee (EmpID, Name) VALUES (101, 'Rohan');
Ans 5:
UPDATE Employee SET Salary = 60000 WHERE EmpID = 101;
Ans 6:
DELETE FROM Employee WHERE Salary < 20000;
Ans 7: DQL retrieves data without altering it, whereas DML adds, modifies, or removes data records in tables.
Ans 8:
SELECT DISTINCT Department FROM Employee;
Ans 9: All rows in the table will have their specified column values updated.
Ans 10: All rows/records will be deleted from the table, leaving the table structure empty.
By Anjeev Kr Singh – Computer Science Educator Published on : September 19, 2026 | Updated on : September 19, 2026
About the Author
Anjeev Kr Singh
Computer Science Educator, Author, and HOD. Guiding CBSE students in CS, IP, IT, WA & AI via mycstutorial.in. Creator of Question Bank for Class 10 & 12 students.
