Data Chronicles with Akshay

Mastering Database Management Systems (DBMS)

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Akshay Anilkumar
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4 min read

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In the world of technology, managing and organizing data efficiently is crucial. Database Management Systems (DBMS) are the backbone of modern applications, allowing seamless data storage, retrieval, and manipulation. In this blog, we’ll explore the fundamentals of DBMS using MySQL, a leading relational database system.

What is DBMS?

A Database Management System (DBMS) is software that facilitates the creation, management, and manipulation of databases. It serves as an intermediary between users, applications, and the database, ensuring:

  • Data Accuracy: Maintains consistency across records.

  • Data Security: Restricts unauthorized access.

  • Efficiency: Optimizes performance for data queries and updates.

Why Use MySQL?

MySQL is a powerful open-source relational database system that supports SQL (Structured Query Language). Key features include:

  • Ease of Integration: Works seamlessly with various programming languages.

  • Scalability: Handles applications from small websites to large-scale systems.

  • Community Support: Vast documentation and an active user community.

SQL vs. MySQL

  • SQL: A standard language for managing relational databases.

  • MySQL: A relational database system that implements SQL commands to manage data.

Think of SQL as a universal toolkit and MySQL as one of the tools using it.

Basic Terminology

  • Database: A structured collection of data.

  • Table: A set of data arranged in rows (records) and columns (attributes).

  • Primary Key: A unique identifier for each record in a table.

  • Foreign Key: An attribute in one table that refers to the primary key in another.

Categories of SQL Commands

  1. DDL (Data Definition Language): Commands for database structure (CREATE, DROP).

  2. DML (Data Manipulation Language): Commands for data handling (INSERT, UPDATE, DELETE).

  3. DQL (Data Query Language): Commands for fetching data (SELECT).

  4. DCL (Data Control Language): Commands for access control (GRANT, REVOKE).

  5. TCL (Transaction Control Language): Commands for transaction management (COMMIT, ROLLBACK).

Database Operations

1. List All Databases

SHOW DATABASES;

2. Create a Database

CREATE DATABASE employee_data;

3. Select a Database

USE employee_data;

4. Verify the Selected Database

SELECT DATABASE();

5. Delete a Database

DROP DATABASE employee_data;

Table Operations

1. Display All Tables in a Database

SHOW TABLES;

2. Create a Table

CREATE TABLE employees (  
    emp_id INT NOT NULL AUTO_INCREMENT,  
    first_name VARCHAR(50),  
    last_name VARCHAR(50),  
    hire_date DATE,  
    salary FLOAT,  
    PRIMARY KEY (emp_id)  
);

3. View Table Details

DESC employees;

4. Modify a Table

Add a Column:

ALTER TABLE employees ADD department VARCHAR(50);

Delete a Column:

ALTER TABLE employees DROP COLUMN department;

Rename a Column:

ALTER TABLE employees CHANGE hire_date joining_date DATE;

Record Operations

1. Insert Data into a Table

INSERT INTO employees (first_name, last_name, hire_date, salary)  
VALUES ('John', 'Doe', '2022-01-15', 60000);

2. Fetch Data from a Table

SELECT * FROM employees;  
SELECT first_name, salary FROM employees WHERE salary > 50000;

3. Update Data in a Table

UPDATE employees  
SET salary = 65000  
WHERE emp_id = 1;

4. Delete a Record from a Table

DELETE FROM employees WHERE emp_id = 1;

Understanding Database Relationships

  • One-to-One: Links one record in a table to one record in another.

  • One-to-Many: Connects a single record in one table to multiple records in another.

  • Many-to-Many: Requires an intermediate table for mapping.

Example of Foreign Key

CREATE TABLE departments (  
    dept_id INT NOT NULL AUTO_INCREMENT,  
    dept_name VARCHAR(50),  
    PRIMARY KEY (dept_id)  
);  

CREATE TABLE employees (  
    emp_id INT NOT NULL AUTO_INCREMENT,  
    first_name VARCHAR(50),  
    last_name VARCHAR(50),  
    dept_id INT,  
    PRIMARY KEY (emp_id),  
    FOREIGN KEY (dept_id) REFERENCES departments(dept_id)  
);

Using SQL JOINs

1. INNER JOIN

Retrieves records that have matching values in both tables.

SELECT employees.first_name, departments.dept_name  
FROM employees  
INNER JOIN departments  
ON employees.dept_id = departments.dept_id;

2. LEFT JOIN

Retrieves all records from the left table and matching records from the right table.

SELECT employees.first_name, departments.dept_name  
FROM employees  
LEFT JOIN departments  
ON employees.dept_id = departments.dept_id;

3. RIGHT JOIN

Retrieves all records from the right table and matching records from the left table.

SELECT employees.first_name, departments.dept_name  
FROM employees  
RIGHT JOIN departments  
ON employees.dept_id = departments.dept_id;

Conclusion

Mastering DBMS concepts and SQL commands is essential for anyone working with data. MySQL, with its user-friendly features, is an excellent choice for managing relational databases. Whether you're creating a small project or an enterprise system, these concepts will empower you to build scalable and efficient solutions.

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