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https://github.com/Asit-14/Mysql-RDBMS-

This Repository contains all the SQL notes related to the course.
https://github.com/Asit-14/Mysql-RDBMS-

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README 

          
# MySQL Complete Guide: From Beginner to Advanced 🚀



A comprehensive guide to MySQL operations with easy-to-understand examples.



## What is MySQL?



MySQL is a widely-used, open-source relational database management system (RDBMS). It is designed to handle a range of applications, from small projects to large-scale enterprise solutions. MySQL is known for its reliability, performance, and ease of use.



## What is RDBMS?



RDBMS stands for Relational Database Management System. It is a software application that enables users to create, manage, and maintain relational databases. RDBMSs use structured query language (SQL) for accessing and manipulating data.



## 📚 Table of Contents

- [Getting Started](#getting-started)

- [Basic Operations](#basic-operations)

- [Working with Tables](#working-with-tables)

- [Data Operations](#data-operations)

- [Querying Data](#querying-data)

- [Advanced Topics](#advanced-topics)

- [Best Practices](#best-practices)



## 🚀 Getting Started



### Connect to MySQL

```sql

mysql -u username -p

```



### Database Management

```sql

-- Create new database

CREATE DATABASE my_app;



-- Show all databases

SHOW DATABASES;



-- Select a database to use

USE my_app;



-- Delete database

DROP DATABASE my_app;

```



## 📋 Basic Operations



### Creating Tables

```sql

-- Simple table

CREATE TABLE students (

    id INT PRIMARY KEY AUTO_INCREMENT,

    name VARCHAR(100),

    age INT

);



-- Table with more specifications

CREATE TABLE users (

    id INT PRIMARY KEY AUTO_INCREMENT,

    username VARCHAR(50) NOT NULL UNIQUE,

    email VARCHAR(100) NOT NULL,

    password VARCHAR(255) NOT NULL,

    created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,

    status ENUM('active', 'inactive') DEFAULT 'active'

);

```



### Table Operations

```sql

-- List all tables

SHOW TABLES;



-- See table structure

DESCRIBE users;



-- Delete table

DROP TABLE users;



-- Modify table

ALTER TABLE users ADD COLUMN phone VARCHAR(15);

ALTER TABLE users DROP COLUMN phone;

```



## 💾 Data Operations



### Adding Data

```sql

-- Insert single row

INSERT INTO users (username, email) 

VALUES ('john_doe', 'john@example.com');



-- Insert multiple rows

INSERT INTO users (username, email) VALUES 

    ('jane_doe', 'jane@example.com'),

    ('bob123', 'bob@example.com');

```



### Reading Data

```sql

-- Select all columns

SELECT * FROM users;



-- Select specific columns

SELECT username, email FROM users;



-- Select with condition

SELECT * FROM users WHERE status = 'active';



-- Select with multiple conditions

SELECT * FROM users 

WHERE status = 'active' 

AND created_at >= '2023-01-01';

```



### Updating Data

```sql

-- Update single record

UPDATE users 

SET status = 'inactive' 

WHERE id = 1;



-- Update multiple records

UPDATE users 

SET status = 'inactive' 

WHERE created_at < '2023-01-01';

```



### Deleting Data

```sql

-- Delete single record

DELETE FROM users WHERE id = 1;



-- Delete with condition

DELETE FROM users WHERE status = 'inactive';



-- Delete all records

TRUNCATE TABLE users;

```



## 🔍 Querying Data



### Basic Queries

```sql

-- Filter with WHERE

SELECT * FROM users WHERE age >= 18;



-- Sort results

SELECT * FROM users ORDER BY username ASC;



-- Limit results

SELECT * FROM users LIMIT 10;



-- Skip and limit (pagination)

SELECT * FROM users LIMIT 10 OFFSET 20;

```



### Pattern Matching

```sql

-- Find usernames starting with 'j'

SELECT * FROM users WHERE username LIKE 'j%';



-- Find emails containing 'example'

SELECT * FROM users WHERE email LIKE '%example%';

```



### Aggregate Functions

```sql

-- Count total users

SELECT COUNT(*) FROM users;



-- Get average age

SELECT AVG(age) FROM users;



-- Find maximum value

SELECT MAX(age) FROM users;



-- Group and count

SELECT status, COUNT(*) as total 

FROM users 

GROUP BY status;

```



## 🎓 Advanced Topics



### Joins

```sql

-- Inner join

SELECT users.username, orders.order_date 

FROM users 

INNER JOIN orders ON users.id = orders.user_id;



-- Left join

SELECT users.username, orders.order_date 

FROM users 

LEFT JOIN orders ON users.id = orders.user_id;

```



### Subqueries

```sql

-- Subquery in WHERE

SELECT * FROM users 

WHERE id IN (SELECT user_id FROM orders);



-- Subquery in SELECT

SELECT username, 

    (SELECT COUNT(*) FROM orders WHERE orders.user_id = users.id) 

    as order_count 

FROM users;

```



### Indexes

```sql

-- Create index

CREATE INDEX idx_username ON users(username);



-- Create unique index

CREATE UNIQUE INDEX idx_email ON users(email);



-- Remove index

DROP INDEX idx_username ON users;

```



### Views

```sql

-- Create view

CREATE VIEW active_users AS 

SELECT * FROM users WHERE status = 'active';



-- Use view

SELECT * FROM active_users;



-- Drop view

DROP VIEW active_users;

```



## 💡 Best Practices



### Performance Tips

1. Always use appropriate data types

2. Create indexes for frequently searched columns

3. Use LIMIT in SELECT queries

4. Avoid SELECT *

5. Use prepared statements for security



### Backup and Restore

```sql

-- Backup database

mysqldump -u username -p database_name > backup.sql



-- Restore database

mysql -u username -p database_name < backup.sql

```



## 🔧 Common Operations



### String Operations

```sql

-- Concatenate strings

SELECT CONCAT(first_name, ' ', last_name) AS full_name FROM users;



-- Convert case

SELECT LOWER(username), UPPER(email) FROM users;

```



### Date Operations

```sql

-- Current date/time

SELECT NOW();



-- Format date

SELECT DATE_FORMAT(created_at, '%Y-%m-%d') FROM users;



-- Date calculations

SELECT username, DATEDIFF(NOW(), created_at) as days_since_joined 

FROM users;

```



### Transactions

```sql

-- Start transaction

START TRANSACTION;



-- Multiple operations

INSERT INTO users (username, email) VALUES ('new_user', 'new@example.com');

UPDATE users SET status = 'active' WHERE username = 'new_user';



-- Commit or rollback

COMMIT;

-- or

ROLLBACK;

```



### SELECT

```sql

SELECT column1, column2 FROM table_name;

SELECT * FROM table_name;

```



### WHERE

```sql

SELECT column1, column2 FROM table_name WHERE condition;

SELECT * FROM table_name WHERE age >= 18;

```



### AND, OR, NOT

```sql

SELECT * FROM table_name WHERE condition1 AND condition2;

SELECT * FROM table_name WHERE condition1 OR condition2;

SELECT * FROM table_name WHERE NOT condition;

```



### ORDER BY

```sql

SELECT * FROM table_name ORDER BY column1 ASC|DESC;

```



### INSERT INTO

```sql

INSERT INTO table_name (column1, column2) VALUES (value1, value2);

INSERT INTO table_name VALUES (value1, value2);

```



### NULL Values

```sql

SELECT column_names FROM table_name WHERE column_name IS NULL;

SELECT column_names FROM table_name WHERE column_name IS NOT NULL;

```



### UPDATE

```sql

UPDATE table_name SET column1 = value1 WHERE condition;

```



### DELETE

```sql

DELETE FROM table_name WHERE condition;

```



### LIMIT

```sql

SELECT column_names FROM table_name LIMIT number;

```



### MIN and MAX

```sql

SELECT MIN(column_name) FROM table_name;

SELECT MAX(column_name) FROM table_name;

```



### COUNT, AVG, SUM

```sql

SELECT COUNT(column_name) FROM table_name;

SELECT AVG(column_name) FROM table_name;

SELECT SUM(column_name) FROM table_name;

```



### LIKE

```sql

SELECT column1 FROM table_name WHERE column_name LIKE pattern;

-- % represents zero, one, or multiple characters

-- _ represents one single character

```



### Wildcards

```sql

SELECT * FROM table_name WHERE column LIKE 'a%';    -- Starts with a

SELECT * FROM table_name WHERE column LIKE '%a';    -- Ends with a

SELECT * FROM table_name WHERE column LIKE '%a%';   -- Contains a

```



### IN

```sql

SELECT * FROM table_name WHERE column_name IN (value1, value2);

```



### BETWEEN

```sql

SELECT * FROM table_name WHERE column_name BETWEEN value1 AND value2;

```



### Aliases

```sql

SELECT column_name AS alias_name FROM table_name;

SELECT column_name alias_name FROM table_name;

```



### Joins

#### INNER JOIN

```sql

SELECT columns FROM table1 INNER JOIN table2 ON table1.column = table2.column;

```



#### LEFT JOIN

```sql

SELECT columns FROM table1 LEFT JOIN table2 ON table1.column = table2.column;

```



#### RIGHT JOIN

```sql

SELECT columns FROM table1 RIGHT JOIN table2 ON table1.column = table2.column;

```



#### CROSS JOIN

```sql

SELECT columns FROM table1 CROSS JOIN table2;

```



#### Self Join

```sql

SELECT columns FROM table1 T1, table1 T2 WHERE condition;

```



### UNION

```sql

SELECT columns FROM table1 UNION SELECT columns FROM table2;

```



### GROUP BY

```sql

SELECT column_name, aggregate_function(column_name)

FROM table_name

GROUP BY column_name;

```



### HAVING

```sql

SELECT column_name, aggregate_function(column_name)

FROM table_name

GROUP BY column_name

HAVING condition;

```



### EXISTS

```sql

SELECT column_name FROM table_name

WHERE EXISTS (SELECT column_name FROM table_name WHERE condition);

```



### ANY, ALL

```sql

SELECT column_name FROM table_name

WHERE column_name operator ANY/ALL

(SELECT column_name FROM table_name WHERE condition);

```



### INSERT SELECT

```sql

INSERT INTO table2 SELECT * FROM table1;

```



### CASE

```sql

SELECT 

    CASE

        WHEN condition1 THEN result1

        WHEN condition2 THEN result2

        ELSE result3

    END

FROM table_name;

```



### Null Functions

```sql

SELECT IFNULL(column_name, 'Alternative value') FROM table_name;

SELECT COALESCE(value1, value2, ..., value_n);

```



### Comments

```sql

-- Single line comment

/* Multi-line

   comment */

```



## Database Operations



### Create Database

```sql

CREATE DATABASE database_name;

```



### Drop Database

```sql

DROP DATABASE database_name;

```



### Create Table

```sql

CREATE TABLE table_name (

    column1 datatype constraint,

    column2 datatype constraint,

    column3 datatype constraint

);

```



### Drop Table

```sql

DROP TABLE table_name;

```



### Alter Table

```sql

ALTER TABLE table_name ADD column_name datatype;

ALTER TABLE table_name DROP COLUMN column_name;

ALTER TABLE table_name MODIFY COLUMN column_name datatype;

```



### Constraints

```sql

-- NOT NULL

column_name datatype NOT NULL



-- UNIQUE

column_name datatype UNIQUE



-- PRIMARY KEY

column_name datatype PRIMARY KEY



-- FOREIGN KEY

FOREIGN KEY (column_name) REFERENCES table_name(column_name)



-- CHECK

CHECK (condition)



-- DEFAULT

column_name datatype DEFAULT value

```



### Create Index

```sql

CREATE INDEX index_name ON table_name (column1, column2);

```



### Auto Increment

```sql

column_name datatype AUTO_INCREMENT

```



### Views

```sql

CREATE VIEW view_name AS

SELECT column1, column2

FROM table_name

WHERE condition;

```



## References



### Common Data Types

- INT - Integer

- DECIMAL(size,d) - Decimal numbers

- CHAR(size) - Fixed-length string

- VARCHAR(size) - Variable-length string

- TEXT - String with maximum length of 65,535 characters

- DATE - Date in YYYY-MM-DD format

- DATETIME - Date and time combination

- TIMESTAMP - Timestamp

- BOOLEAN - True or False



### Common Functions

- String Functions: CONCAT(), SUBSTRING(), TRIM(), UPPER(), LOWER()

- Numeric Functions: ROUND(), CEIL(), FLOOR(), ABS()

- Date Functions: NOW(), CURDATE(), DATEDIFF(), DATE_FORMAT()

- Aggregate Functions: COUNT(), SUM(), AVG(), MIN(), MAX()



### MySQL Functions

- String: CONCAT(), SUBSTRING(), TRIM()

- Numeric: ROUND(), CEIL(), FLOOR()

- Date: NOW(), CURDATE(), DATE_FORMAT()

- Aggregate: COUNT(), SUM(), AVG(), MIN(), MAX()



### MySQL Operators

- Arithmetic: +, -, *, /, %

- Comparison: =, >, <, >=, <=, <>

- Logical: AND, OR, NOT

- Pattern Matching: LIKE, IN, BETWEEN



---

## Contributing



We welcome contributions! If you have suggestions or improvements, please submit a pull request.

## Contact



For any questions or feedback, please reach out to [asitshakya789@gmail.com](mailto:asitshakya789@gmail.com).

## Thank You!



Thank you for taking the time to read this guide. Happy coding!