Chapter 2: Database Management System

How we store, organise and retrieve information: from a school register to MySQL and SQL queries, with real Nepali examples.

1 Introduction

Every day around us, huge amounts of information are stored and used. When you go to Nabil Bank to withdraw money, when your school keeps the marks of every student, when Daraz shows your past orders, or when Nepal Telecom stores the numbers of millions of customers: all of this is possible because of databases.

A Database Management System (DBMS) is special software that helps us store this information in an organised way and get it back quickly whenever we need it. In this chapter we will learn what data is, how it becomes information, what a database and DBMS are, and how to actually create and use a database with MySQL and SQL commands.

Real example: Imagine the office register of your school written by hand. Finding one student among 2,000 takes a long time. A database does the same job but finds the student in less than a second.

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Image: Data all around us (bank, school, shop)

Place your image here (filename: dbms-intro.png)

2 Importance of Database

A database is important because it lets organisations keep large amounts of data safe, organised and easy to use. Without databases, modern banks, hospitals, schools and online shops could not work.

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Fast Access

Find any record in seconds, e.g. a patient's report at Bir Hospital.

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Organised Storage

Data is stored neatly in tables instead of scattered papers.

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Security

Only authorised staff can see sensitive data like bank balances.

♻️

No Repetition

The same customer's details are not written again and again.

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Easy Reports

Generate marksheets, bills and summaries automatically.

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Sharing

Many users can use the same data at the same time.

3 Data

Data is a collection of raw facts and figures that have no meaning on their own. Data can be numbers, text, dates, images, audio or video.

Data by itself does not tell us much. For example, the values 85, Sita, Kathmandu are just raw facts: we do not yet know what they mean.

Example: "Ram", "16", "Pokhara", "72" are pieces of data. We cannot make a decision from them until they are organised.

4 Data Processing

Data processing is the act of converting raw data into meaningful information through steps like collecting, organising, calculating, sorting and summarising.

The basic cycle is: Input → Process → Output.

Stage	What happens	School example
Input	Raw data is entered	Marks of each student in every subject are typed in.
Process	Data is calculated/sorted	Total and percentage are calculated; rank is sorted.
Output	Meaningful result is produced	A printed marksheet showing result and division.

5 Information

Information is processed data that is meaningful and useful for making decisions.

When raw data is processed, it becomes information that we can understand and act upon.

Data → Information: The data "Sita", 85, 92, 78 becomes information when processed: "Sita scored 255 marks, 85%, securing 1st position in Class 10." Now it is useful.

Data	Information
Raw, unorganised facts	Processed, organised, meaningful
No clear meaning alone	Helps in decision making
Example: 85, 92, 78	Example: Average mark = 85, First Division

6 Database

Database is an organised collection of related data stored together so that it can be accessed, managed and updated easily.

Think of a database as a digital filing cabinet. Inside it, related data is kept in tables (like separate drawers). For example, a school database may contain a Students table, a Teachers table and a Marks table: all related to the same school.

Real example: The eSewa app stores millions of users, their balances and transaction history inside a database.

7 Database Management System (DBMS)

Database Management System (DBMS) is software that allows users to create, store, organise, retrieve, update and manage data in a database.

The DBMS sits between the user and the database. The user gives simple commands (like "show all students of Grade 10") and the DBMS takes care of finding and returning the data.

Popular DBMS software

MySQL: free, open-source, very popular for websites.
Microsoft Access: easy, used in schools and small offices.
Oracle: used by big banks and companies.
Microsoft SQL Server, PostgreSQL, MongoDB: other widely used systems.

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Image: User → DBMS → Database

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8 Features of DBMS

📁

Data Storage

Stores large amounts of data in an organised manner.

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Data Retrieval

Quickly searches and returns required data using queries.

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Security

Provides usernames, passwords and permissions.

👨‍👩‍👧

Multi-User

Many users can access data at the same time.

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Backup & Recovery

Automatically backs up and recovers data after failure.

✅

Data Integrity

Keeps data accurate and consistent using rules.

9 Advantages of DBMS

Controls data redundancy: the same data is not repeated, saving space.
Data consistency: when data is updated in one place, it stays correct everywhere.
Data sharing: many users and programs can share the same data.
Better security: access can be limited to authorised users only.
Fast access: data is found quickly using queries.
Backup and recovery: protects data from loss.
Easy reports: marksheets, bills and summaries are generated automatically.

10 Disadvantages of DBMS

High cost: good DBMS software and hardware can be expensive.
Complex: it is difficult to design and manage large databases.
Needs trained staff: a database administrator (DBA) is required.
Risk of failure: if the system crashes, many users are affected.
Security risk: if hacked, a lot of data can be stolen at once.

11 Types of DBMS

DBMS are classified according to how they organise data.

Type	How data is organised	Example
Hierarchical DBMS	Data in a tree (parent–child) structure	IBM IMS
Network DBMS	Data connected like a network (many links)	IDMS
Relational DBMS (RDBMS)	Data in tables (rows & columns)	MySQL, Oracle
Object-Oriented DBMS	Data stored as objects	db4o, ObjectDB

Note: The Relational type is the most common today and is what we use with MySQL.

12 Relational DBMS (RDBMS)

Relational DBMS (RDBMS) is a type of DBMS that stores data in the form of tables (rows and columns) and allows tables to be related to one another using keys.

It was based on the relational model proposed by E. F. Codd. Each table holds data about one subject (e.g. students), and tables can be linked together. Examples: MySQL, Oracle, SQL Server, PostgreSQL, MS Access.

Why "relational"? Because tables can be related to each other: e.g. a Marks table is related to a Students table through the student's roll number.

13 Difference Between DBMS and RDBMS

DBMS	RDBMS
Stores data as files	Stores data in tables (rows & columns)
No relationship between data	Tables can be related using keys
Handles small amounts of data	Handles large amounts of data
Usually single user	Supports many users at once
Less security	More security and data integrity
Example: older/file-based systems	Example: MySQL, Oracle, SQL Server

14 Data Types

Data type defines what kind of value a field (column) can store, e.g. text, numbers or dates.

Choosing the right data type is important. A phone number, a name, a price and a date of birth all need different data types. The main groups are String, Numeric, and Date & Time.

15 String Data Types

String data types store text (letters, words, sentences).

Data Type	Use	Example value
CHAR(size)	Fixed-length text. Always uses the given size.	Country code `"NP"`
VARCHAR(size)	Variable-length text. Uses only the space needed (most common).	Name `"Sita Sharma"`
TEXT(size)	Larger text such as a paragraph.	Student remarks / address
LONGTEXT	Very large text (up to 4 GB).	A full article or notice

Tip: Use VARCHAR for names and addresses because they vary in length. Use CHAR only when length is fixed, like a 2-letter code.

16 Numeric Data Types

Numeric data types store numbers used for counting and calculation.

Data Type	Use	Example value
INT	Whole numbers	Roll number `25`
SMALLINT	Small whole numbers (limited range)	Age `16`
BIGINT	Very large whole numbers	Citizenship / account no.
DECIMAL(p,s)	Exact numbers with decimals (best for money)	Price `1250.50`
FLOAT	Approximate decimal numbers	Percentage `84.75`

Money tip: Always use DECIMAL for rupees and prices so rounding errors do not happen.

17 Date and Time Data Types

Data Type	Stores	Format / Example
DATE	A date only	2026-05-29 (YYYY-MM-DD)
TIME	A time only	14:30:00
DATETIME	Date and time together	2026-05-29 14:30:00
YEAR	A year only	2026

Example: A student's date of birth uses DATE, while an eSewa transaction time uses DATETIME.

18 Field

Field (also called a column or attribute) is a single piece of information about one subject. It is a vertical column in a table.

In a Students table, each piece of information is a field: Roll_No, Name, Class, Address, Phone. Every field stores one type of data.

19 Record (Row / Tuple)

Record is a complete set of related fields about one item. It is a horizontal row in a table and is also called a tuple.

One full row about a single student is one record.

Roll_No	Name	Class	Address
1	Sita Sharma	10	Lalitpur
2	Ram Thapa	10	Bhaktapur

Remember: A field is a column (e.g. Name). A record is a row (e.g. all details of Sita). The highlighted row above is one record/tuple.

20 Table

Table (also called a relation) is a collection of related records arranged in rows and columns. It is the basic structure for storing data in an RDBMS.

A table has a name (e.g. Students), columns (fields) and rows (records). One database can contain many tables.

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Image: Table = Fields (columns) + Records (rows)

Place your image here (filename: table-structure.png)

21 Database System

Database System is the combination of hardware, software (DBMS), data, users and procedures that work together to store and manage data.

Main components

Hardware: computers, servers, storage where the database runs.
Software: the DBMS (e.g. MySQL) and operating system.
Data: the actual information stored in tables.
Users: database administrator, programmers and end users.
Procedures: the rules and instructions for using the system.

22 Keys

Key is a field (or set of fields) used to uniquely identify a record in a table and to create relationships between tables.

Without a key, two students with the same name "Ram Thapa" could be confused. A key (like Roll Number) makes each record unique and easy to find.

23 Types of Keys

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Primary Key

A field that uniquely identifies each record. It cannot be empty (NULL) or repeated. Example: Roll_No in Students.

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Foreign Key

A field that links one table to the primary key of another table. Example: Roll_No in the Marks table linking to Students.

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Composite Key

A key made of two or more fields together, used when one field alone cannot be unique. Example: Roll_No + Subject.

Nepali example: In a citizenship database, the citizenship number is a primary key: no two people share it.

24 Relationships

A relationship shows how records in one table are connected to records in another table.

Relationship	Meaning	Nepali example
One to One (1:1)	One record links to exactly one record	One citizen has one citizenship number.
One to Many (1:M)	One record links to many records	One class has many students.
Many to One (M:1)	Many records link to one record	Many students belong to one school.
Many to Many (M:M)	Many records link to many records	Many students study many subjects.

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Image: Types of relationships diagram

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25 Introduction to MySQL

MySQL is a free, open-source Relational Database Management System (RDBMS) that uses SQL to store and manage data.

MySQL is one of the most popular databases in the world. It is used by websites and apps like Facebook and YouTube, and by many Nepali companies for their software. It is free, fast and works on Windows, Linux and macOS.

Note: MySQL was created by a Swedish company and is now owned by Oracle. "SQL" stands for Structured Query Language: the language we use to talk to the database.

26 Features of MySQL

🆓

Free & Open Source

Anyone can download and use it without cost.

⚡

Fast & Reliable

Handles large data quickly with high performance.

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Cross-Platform

Runs on Windows, Linux and macOS.

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Secure

Supports passwords and user permissions.

👥

Multi-User

Many users can work at the same time.

🌐

Web Friendly

Works perfectly with PHP for websites.

27 Installing MySQL

The easiest way for students is to install XAMPP, which includes MySQL, or to install MySQL Community Server with MySQL Workbench.

Simple steps (using XAMPP)

Go to apachefriends.org and download XAMPP for Windows.
Run the installer and click Next until finished.
Open the XAMPP Control Panel.
Click Start next to Apache and MySQL.
Open a browser and go to http://localhost/phpmyadmin.
Now you can create databases and run SQL queries.

Tip: phpMyAdmin gives you a friendly screen to create tables by clicking, and also a box to type SQL queries directly.

28 Query (Select, Update, Delete)

Query is a request or command given to the database to perform a task such as showing, adding, changing or removing data.

We will use a sample Students table for the examples below.

Select Query

Used to view / fetch data from a table.

SQL

-- Show all students SELECT * FROM Students; -- Show only name and class of Grade 10 students SELECT Name, Class FROM Students WHERE Class = 10;

Update Query

Used to change / edit existing data.

SQL

-- Change Ram's address to Kathmandu UPDATE Students SET Address = 'Kathmandu' WHERE Roll_No = 2;

Delete Query

Used to remove records from a table.

SQL

-- Remove the student with Roll_No 5 DELETE FROM Students WHERE Roll_No = 5;

Warning: Always use WHERE with UPDATE and DELETE. Without it, all records get changed or deleted!

29 SQL and its Features

SQL (Structured Query Language) is the standard language used to create, manage and work with data in a relational database.

Features of SQL

Simple, English-like commands (SELECT, INSERT, UPDATE).
Works with almost all RDBMS (MySQL, Oracle, SQL Server).
Can create databases, tables and define rules.
Can insert, update, delete and fetch data.
Can control security and user permissions.

Main SQL command groups: DDL (structure), DML (data), DCL (permissions), TCL (transactions). For Class 10 we focus on DDL and DML.

30 DDL Commands

DDL (Data Definition Language) commands are used to define and change the structure of a database and its tables.

Command	Use
CREATE	Creates a database or table
ALTER	Adds, changes or deletes a column
DROP	Deletes a whole table or database
TRUNCATE	Removes all records but keeps the empty table

SQL

-- CREATE a database and a table CREATE DATABASE SchoolDB; USE SchoolDB; CREATE TABLE Students ( Roll_No INT PRIMARY KEY, Name VARCHAR(50), Class INT, Address VARCHAR(50) ); -- ALTER: add a new column ALTER TABLE Students ADD Phone VARCHAR(10); -- TRUNCATE: empty the table TRUNCATE TABLE Students; -- DROP: delete the whole table DROP TABLE Students;

31 DML Commands

DML (Data Manipulation Language) commands are used to work with the data inside tables: adding, viewing, changing and removing records.

INSERT: add new records

SQL

INSERT INTO Students (Roll_No, Name, Class, Address) VALUES (1, 'Sita Sharma', 10, 'Lalitpur'); INSERT INTO Students (Roll_No, Name, Class, Address) VALUES (2, 'Ram Thapa', 10, 'Bhaktapur');

SELECT, WHERE, LIKE, ORDER BY

SQL

-- All records SELECT * FROM Students; -- WHERE: students from Lalitpur SELECT * FROM Students WHERE Address = 'Lalitpur'; -- LIKE: names starting with 'S' SELECT * FROM Students WHERE Name LIKE 'S%'; -- ORDER BY: sort names A to Z SELECT * FROM Students ORDER BY Name ASC;

UPDATE and DELETE

SQL

UPDATE Students SET Class = 11 WHERE Roll_No = 1; DELETE FROM Students WHERE Roll_No = 2;

LIKE wildcards: % means "any number of characters" and _ means "exactly one character". So '_a%' means the second letter is 'a'.

32 SQL Constraints

Constraints are rules applied to a column to control what kind of data can be stored, keeping the data correct and reliable.

Constraint	Meaning	Example
NOT NULL	Field cannot be left empty	Name must be entered.
UNIQUE	No two rows can have the same value	Email or phone must be unique.
CHECK	Value must satisfy a condition	Age must be > 0.
DEFAULT	A default value if none is given	Country defaults to 'Nepal'.

SQL

CREATE TABLE Students ( Roll_No INT PRIMARY KEY, Name VARCHAR(50) NOT NULL, Phone VARCHAR(10) UNIQUE, Age INT CHECK (Age > 0), Country VARCHAR(30) DEFAULT 'Nepal' );

33 Primary Key

Primary Key is a special constraint that uniquely identifies each record in a table. It is always NOT NULL and UNIQUE.

A table can have only one primary key. It is the most important key because every other table connects to it.

SQL

CREATE TABLE Students ( Roll_No INT PRIMARY KEY, Name VARCHAR(50) );

Real example: In a Nepali bank, the account number is the primary key. No two accounts can have the same number.

34 Operators Supported by SQL

An operator is a symbol or keyword used to perform an operation on values. SQL supports four main groups: Arithmetic, Relational/Comparison, Logical and Special operators.

35 Arithmetic Operator

Used to perform calculations on numeric data.

Operator	Meaning	Example
+	Addition	Marks1 + Marks2
-	Subtraction	Price - Discount
*	Multiplication	Qty * Rate
/	Division	Total / 5
%	Modulus (remainder)	Roll_No % 2

SQL

-- Total marks of each student SELECT Name, (English + Nepali + Math) AS Total FROM Marks;

36 Relational / Comparison Operator

Used to compare two values; the result is true or false.

Operator	Meaning	Example
=	Equal to	Class = 10
>	Greater than	Marks > 40
<	Less than	Age < 18
>=	Greater than or equal	Marks >= 80
<=	Less than or equal	Price <= 1000
<> or !=	Not equal to	Class <> 9

SQL

-- Students who passed (marks 40 or above) SELECT Name FROM Marks WHERE Total >= 40;

37 Logical Operator

Used to combine two or more conditions.

Operator	Meaning
AND	Both conditions must be true
OR	At least one condition must be true
NOT	Reverses the condition (true ↔ false)

SQL

-- Grade 10 students from Lalitpur SELECT * FROM Students WHERE Class = 10 AND Address = 'Lalitpur'; -- Students from Lalitpur OR Bhaktapur SELECT * FROM Students WHERE Address = 'Lalitpur' OR Address = 'Bhaktapur';

38 Special Operators

Operator	Meaning	Example
BETWEEN	Within a range (inclusive)	Marks BETWEEN 40 AND 60
IN	Matches any value in a list	Address IN ('Lalitpur','Pokhara')
LIKE	Pattern matching with % and _	Name LIKE 'R%'
IS NULL	Field has no value	Phone IS NULL

SQL

SELECT * FROM Marks WHERE Total BETWEEN 40 AND 60; SELECT * FROM Students WHERE Address IN ('Lalitpur', 'Pokhara', 'Biratnagar');

39 Reports and Types of Reports

Report is a neatly formatted output of data from a database, presented in a way that is easy to read and print, such as a marksheet or a bill.

Types of Reports

📄

Summary Report

Shows totals and key figures only. E.g. total students passed and failed.

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Detail Report

Shows every record in full. E.g. complete list of all students with marks.

🗂️

Grouped Report

Data grouped by a category. E.g. students grouped by class or district.

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Filtered Report

Shows only records meeting a condition. E.g. only failed students.

Advantages of Reports

Present data in a clear, professional, printable format.
Help managers and teachers make quick decisions.
Save time as they are generated automatically.
Can summarise thousands of records into a single page.
Reduce errors compared to writing by hand.

40 Real-Life Example with Queries

Let us build a small School Result System from start to finish: exactly how a Nepali school could store and use student marks.

Step 1: Create the database and tables

SQL

CREATE DATABASE SchoolDB; USE SchoolDB; CREATE TABLE Students ( Roll_No INT PRIMARY KEY, Name VARCHAR(50) NOT NULL, Class INT, Address VARCHAR(50) DEFAULT 'Nepal' ); CREATE TABLE Marks ( Roll_No INT, English INT, Nepali INT, Math INT, FOREIGN KEY (Roll_No) REFERENCES Students(Roll_No) );

Step 2: Insert data

SQL

INSERT INTO Students VALUES (1, 'Sita Sharma', 10, 'Lalitpur'), (2, 'Ram Thapa', 10, 'Bhaktapur'), (3, 'Gita Rai', 10, 'Dharan'); INSERT INTO Marks VALUES (1, 85, 90, 80), (2, 35, 60, 45), (3, 70, 65, 88);

Step 3: Useful queries (reports)

SQL

-- Detail report: every student's total and percentage SELECT s.Roll_No, s.Name, (m.English + m.Nepali + m.Math) AS Total, (m.English + m.Nepali + m.Math) / 3 AS Percentage FROM Students s JOIN Marks m ON s.Roll_No = m.Roll_No ORDER BY Total DESC; -- Filtered report: students who failed (any subject below 40) SELECT s.Name FROM Students s JOIN Marks m ON s.Roll_No = m.Roll_No WHERE m.English < 40 OR m.Nepali < 40 OR m.Math < 40; -- Summary report: how many students in total SELECT COUNT(*) AS Total_Students FROM Students; -- Search report: find a student by name SELECT * FROM Students WHERE Name LIKE '%Sharma%';

What you just built: A real result system. The same idea powers college admission systems, eSewa transactions and hospital records: only the table names and fields change.

📝 Exercises & Quiz

Test what you've learned! Click Show Answer to check yourself.

📚 Short Terms / Glossary

Data

Raw facts and figures with no meaning on their own.

Information

Processed, meaningful data useful for decisions.

Database

Organised collection of related data.

DBMS

Software to create and manage databases.

RDBMS

DBMS that stores data in related tables.

Field

A column; one piece of information.

Record

A row/tuple; one complete set of fields.

Table

Collection of records in rows and columns.

Primary Key

Field that uniquely identifies each record.

Foreign Key

Field linking one table to another's primary key.

Query

A command given to the database.

Constraint

A rule that controls data in a column.

🔤 Full Forms (Click "Reveal" to check)

DBMS Database Management System

RDBMS Relational Database Management System

SQL Structured Query Language

DDL Data Definition Language

DML Data Manipulation Language

DCL Data Control Language

DBA Database Administrator

CHAR Character

VARCHAR Variable Character

INT Integer

✅ Choose the Correct Answer (MCQ)

1. What do we call raw facts that have no meaning on their own?

A Data

B Information

C Report

D Query

2. Which of the following is an RDBMS?

A MS Word

B MySQL

C Photoshop

D Chrome

3. A column in a table is also called a:

A Record

B Tuple

C Field

D Database

4. Which key uniquely identifies each record in a table?

A Primary Key

B Foreign Key

C Composite Key

D Candidate List

5. Which SQL command is used to fetch data from a table?

A INSERT

B SELECT

C CREATE

D DROP

6. Which data type is best to store money/price values?

A VARCHAR

B INT

C DECIMAL

D DATE

7. Which command removes the whole table structure?

A DELETE

B TRUNCATE

C DROP

D ALTER

8. Which constraint makes sure a field is never left empty?

A UNIQUE

B NOT NULL

C DEFAULT

D CHECK

9. Which operator is used for pattern matching in SQL?

A BETWEEN

B IN

C LIKE

D AND

10. "One class has many students" is which type of relationship?

A One to One

B One to Many

C Many to One

D Many to Many

✍️ Short Answer Questions

1 What is data? How is it different from information?

Answer: Data is raw facts and figures with no clear meaning (e.g. 85, Sita). Information is processed, organised data that is meaningful and useful for decisions (e.g. "Sita scored 85% and stood first").

2 Define DBMS and write any two advantages.

Answer: DBMS is software used to create, store, manage and retrieve data in a database. Advantages: controls data redundancy, provides security, allows data sharing, gives fast access, supports backup and recovery (any two).

3 Differentiate between DBMS and RDBMS.

Answer: A DBMS may store data as files with no relationship between them, while an RDBMS stores data in tables that can be related using keys. RDBMS supports more users, larger data and better security than a simple DBMS.

4 Define field, record and table.

Answer: A field is a single column (one piece of information). A record (row/tuple) is a complete set of related fields about one item. A table is a collection of such records arranged in rows and columns.

5 What is a primary key? How is it different from a foreign key?

Answer: A primary key uniquely identifies each record in a table and cannot be NULL or repeated. A foreign key is a field in one table that links to the primary key of another table to create a relationship.

6 Differentiate between DDL and DML with examples.

Answer: DDL (Data Definition Language) defines the structure of tables: CREATE, ALTER, DROP, TRUNCATE. DML (Data Manipulation Language) works with the data inside tables: INSERT, SELECT, UPDATE, DELETE.

7 Write SQL to create a table named Students with Roll_No (primary key) and Name.

Answer: CREATE TABLE Students (Roll_No INT PRIMARY KEY, Name VARCHAR(50));

8 What are SQL constraints? Name any three.

Answer: Constraints are rules applied to columns to keep data correct. Examples: NOT NULL, UNIQUE, CHECK, DEFAULT, PRIMARY KEY (any three).

9 Explain the four types of relationships with one example each.

Answer: One-to-One (one citizen → one citizenship number), One-to-Many (one class → many students), Many-to-One (many students → one school), Many-to-Many (many students study many subjects).

10 Write SQL to show all students of Class 10 from Lalitpur.

Answer: SELECT * FROM Students WHERE Class = 10 AND Address = 'Lalitpur';

11 What is a report? Write its four types.

Answer: A report is a neatly formatted output of database data that is easy to read and print. Types: Summary, Detail, Grouped and Filtered reports.

12 Name the four groups of SQL operators with one example each.

Answer: Arithmetic (+), Relational/Comparison (>), Logical (AND), Special (BETWEEN, LIKE, IN, IS NULL).

🛠️ Practical Ideas (Try in the lab)

Install XAMPP and open phpMyAdmin in your browser at localhost/phpmyadmin.
Create a database named SchoolDB and a Students table with Roll_No, Name, Class and Address.
Insert 5 records of your real classmates using the INSERT command.
Run a SELECT query to display all students, then sort them by name using ORDER BY.
Use WHERE and LIKE to find students whose name starts with a certain letter.
Build a Marks table linked to Students with a foreign key, and write a query to calculate total marks.
Update and Delete: change one student's address, then delete one record (always with WHERE!).
Make a report: write a query to list only students who passed (total >= 120).