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Ch 4-RDBMS

School Revise · Class 11 Information Technology · Chapter 4

RDBMS

Code 802, Class 11. A relational database keeps data in tables and SQL talks to it. Here we meet the relational model and write queries.

table

a relation

SQL

talks to the data

What this chapter is about

An RDBMS (Relational Database Management System) stores data in tables. SQL is the language used to create, add to and question the data.

1. The relational model

A relation is a table, a tuple is a row and an attribute is a column. A primary key uniquely identifies each row, and a foreign key links tables.

2. Writing queries

SELECT reads data, WHERE filters rows and ORDER BY sorts. Aggregate functions COUNT, SUM, AVG, MAX and MIN summarise data.

SELECT name FROM STUDENT WHERE marks > 80; (shows names of students who scored above 80)

3. Changing data

CREATE TABLE makes a table, INSERT adds a row, UPDATE changes values and DELETE removes rows.

Practise with the interactive

Explore the idea by tapping. The interactive opens right here in the lesson.

Coding practice problems, with answers

Type each one into the code lab above, then open the card to see the worked solution and its output.

Problem 1. Show all rows of the STUDENT table.

SOLUTION

SELECT * FROM STUDENT;

OUTPUT

all rows and columns of STUDENT
Problem 2. Show only the names.

SOLUTION

SELECT name FROM STUDENT;

OUTPUT

the name column
Problem 3. Show students who scored above 80.

SOLUTION

SELECT name FROM STUDENT WHERE marks > 80;

OUTPUT

names with marks above 80
Problem 4. Sort by marks, highest first.

SOLUTION

SELECT * FROM STUDENT ORDER BY marks DESC;

OUTPUT

rows sorted by marks, largest first
Problem 5. Count the students.

SOLUTION

SELECT COUNT(*) FROM STUDENT;

OUTPUT

the number of rows
Problem 6. Find the average marks.

SOLUTION

SELECT AVG(marks) FROM STUDENT;

OUTPUT

the average of marks
Problem 7. Create a table.

SOLUTION

CREATE TABLE STUDENT (rollno INT PRIMARY KEY, name VARCHAR(20), marks INT);

OUTPUT

an empty STUDENT table
Problem 8. Insert a row.

SOLUTION

INSERT INTO STUDENT VALUES (1, “Ravi”, 82);

OUTPUT

one row is added
Problem 9. Update a mark.

SOLUTION

UPDATE STUDENT SET marks = 95 WHERE rollno = 1;

OUTPUT

marks of roll number 1 becomes 95
Problem 10. Delete a row.

SOLUTION

DELETE FROM STUDENT WHERE rollno = 1;

OUTPUT

the row with roll number 1 is removed

Practice set A, multiple choice

1. A row of a table is a …

tuple.

2. Which command reads data?

SELECT.

3. Which clause filters rows?

WHERE.

4. Which key links two tables?

A foreign key.

Quick summary

An RDBMS stores data in tables and SQL talks to it. A relation is a table, a tuple a row and an attribute a column; a primary key identifies each row and a foreign key links tables. SELECT reads data, WHERE filters, ORDER BY sorts, and COUNT, SUM, AVG, MAX and MIN summarise. CREATE, INSERT, UPDATE and DELETE build and change the data.
Open the Virtual Lab

These free Class 11 Information Technology (Code 802) notes explain RDBMS and the relational model, tuples and attributes, primary and foreign keys, and SQL SELECT WHERE ORDER BY and aggregate functions with worked examples and practice, for CBSE students across India and the Gulf including the UAE, Saudi Arabia, Qatar, Oman, Kuwait and Bahrain.

© 2026 School Revise. All rights reserved. Original content aligned to the CBSE and NCERT Class 11 Information Technology syllabus. Unauthorised copying is not permitted.

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