CBSE Class 8 Computer Science Sample Paper Set 05

Q1) Define any two of the following:
Query, Database, Referential Integrity [2 Marks]

Answer:
1. Query: A query is a database object that helps us to retrieve, view, and manipulate data from one or more tables based on specific conditions.
2. Database: A database is an organized collection of structured information or data stored electronically in a computer system.
3. Referential Integrity: It is a system of rules used by a Database Management System to ensure that relationships between records in related tables remain valid.

Teacher's Note:
a) Students can attempt any two terms as per the question requirement.
b) Clear definitions with core database terminology are essential for full marks.
c) Referential integrity prevents orphan records in relational tables.

Q2) Differentiate between:
1) Data and Information
2) Master and Slave table
3) Front end and Back end [6 Marks]

Answer:

Teacher's Note:
a) Tabular format is ideal for differentiation questions.
b) Each comparison must cover clear opposing characteristics.
c) Master and slave tables are fundamental to establishing one-to-many relationships.

Q3) Answer the following questions briefly:
1) Give shortcut key to run a query in LibreOffice Base.
2) What is the need of arranging data in more than one table?
3) List any 4 possible attributes of a Teacher table.
4) Give any 2 examples of RDBMS. [8 Marks]

Answer:
1. Shortcut key to run a query in LibreOffice Base is F5.
2. Arranging data in more than one table helps to reduce data redundancy, prevent data anomalies, and maintain data integrity.
3. 4 possible attributes of a Teacher table are Teacher_ID, Teacher_Name, Subject, and Salary.
4. Two examples of RDBMS are MySQL and Oracle.

Teacher's Note:
a) All four sub-parts carry 2 marks each.
b) Ensure standard RDBMS software names are spelled correctly.
c) Attribute names should reflect realistic database fields.

Q4) Identify the valid field names from the following:
"cust_id" , Address, cust-id, order_number, Age [2 Marks]

Answer:
1. Valid field names are: Address, order_number, and Age (also "cust_id" if quotes are considered part of identification, though standard identifiers without special symbols like hyphens are preferred).
2. Invalid names: cust-id (contains a hyphen which acts as a minus operator in expressions).

Teacher's Note:
a) Field names generally should not contain spaces or mathematical operators like hyphens.
b) Check for correct identification of valid identifiers in database naming conventions.

Q5) List errors (if any) in the following SQL statements:-
1) Select from Customer *
2) Select "Cust_id", "Address" from Customer
3) Select orderNo from customer where id 2
4) Select* where id = c007 and age=45 [4 Marks]

Answer:
1. Error: Incorrect syntax order. It should be Select * from Customer.
2. No error: The query is syntactically correct.
3. Error: Missing comparison operator after id. It should be where id = 2.
4. Error: Missing FROM clause and string literal quotes around c007. It should be Select * from table_name where id = 'c007' and age = 45.

Teacher's Note:
a) SQL syntax is strict regarding clause order (SELECT ... FROM ... WHERE).
b) Text values in conditions must be enclosed in single or double quotes.
c) Asterisk (*) must follow the SELECT keyword directly.

Q6) Briefly describe the advantages of DBMS. [2 Marks]

Answer:
1. Reduces data redundancy by storing data in a centralized repository.
2. Ensures data security and provides data sharing among authorized users.

Teacher's Note:
a) Mention at least two core advantages for full marks.
b) Data consistency is another major benefit of DBMS over traditional file systems.

Q7) Explain any 2 Integer data types available in LibreOffice Base. [2 Marks]

Answer:
1. TINYINT: Stores very small integers ranging from 0 to 255 or -128 to 127, occupying 1 byte of storage.
2. INTEGER (or INT): Stores standard whole numbers, typically occupying 4 bytes of storage.

Teacher's Note:
a) Integer data types store whole numbers without decimal points.
b) Mentioning storage size or range adds technical accuracy.

Q8) Define a Report. What is the need of creating Reports? [2 Marks]

Answer:
1. A Report is a database object used to format, calculate, print, and summarize selected data from tables or queries.
2. The need for creating reports is to present data in a professional, readable, and printable format for business decision making.

Teacher's Note:
a) Reports organize data specifically for printing and presentation.
b) They pull information from tables or queries.

Q9) What is a data type? How is char data type different from a varchar? [2 Marks]

Answer:
1. A data type is an attribute that specifies the type of data (like integer, text, date) that an object can hold.
2. CHAR is a fixed-length data type (pads with spaces if the string is shorter than defined), whereas VARCHAR is a variable-length data type (uses only the space required by the actual string).

Teacher's Note:
a) Data types define the domain of values a field can accept.
b) Memory efficiency is the main difference between CHAR and VARCHAR.

Q10) Explain the role of a Database administrator. [2 Marks]

Answer:
1. A Database Administrator (DBA) is responsible for installing, configuring, upgrading, and maintaining the database system.
2. They ensure database security, user access control, performance tuning, and regular data backup and recovery.

Teacher's Note:
a) DBA acts as the custodian of organizational data.
b) Security and backup are key responsibilities.

Q11) Describe the components of the database system. [3 Marks]

Answer:
1. Hardware: The physical computer and storage devices used to store and access the database.
2. Software: The DBMS software itself along with the operating system and network software.
3. Data and Procedures: The actual stored data and the documented rules/instructions for using the system.

Teacher's Note:
a) A complete database system comprises hardware, software, data, procedures, and people (users/DBA).
b) Explaining three major components satisfies the 3-mark requirement.