DEV Community: THE NOID

WHAT IS SQL ?

THE NOID — Sun, 09 Aug 2026 13:20:58 +0000

SQL stands for Structured Query Language. It is used to design and manage data in databases.

EXPLANATION :

Every application which we using today works with data.

Our instagram profile, Amazon orders, Bank Transactions, and even our YouTube history is stored somewhere.

But storing data is only one part of the problem. We also need a way to find, update, and manage that data.

This is where SQL comes in.

FOR EXAMPLE :

Get all users from a database
Add a new customer
Change a user's information
Delete Records
Find specific data

UNDERSTANDING DATABASE :

Before learning SQL, we need to understand what a database is :

A database is a place where information is stored, organized, and managed so that we can easily find, use, and update it whenever needed.

NOTE : We can create multiple databases and each database can contain multiple tables.

We can create databases inside a Database Management System [ DBMS ] or Relational Database Management System [ RDBMS ].

UNDERSTANDING DBMS & RDBMS :

DBMS : A Database Management System is software that helps use to store, organize, and manage data in database easily but it's non relational.

Ex : Microsoft Access, SQLite, MongoDB

RDBMS : An RDBMS is a type of DBMS that stores data in tables and connects realted tables using relationship.

It is smaller subset of DBMS and designed by E.F. Codd in 1970.

Ex : Oracle Database, MySQL, Microsoft SQL Server

TYPES OF SQL :

HOW TO PRACTICE : [ MY APPROACH ]

YouTube Channel : LEARN CODING SQL
Practice Platform : SQL BOLT, HACKERRANK SQL

SQLPLUS INSTALLATION AND SETUP GUIDE :

I used SQLPlus in the Command Prompt because it helps me practice more. Unlike tools like Oracle SQL Developer or MySQL Workbench, you can't easily edit your queries in SQLPlus. Everything is done in the Command Prompt. If you make a mistake, you have to type the query again instead of editing it. This gives you more practice and helps you improve your SQL skills.

Steps :

Browse this link : SQL PLUS
Download the Oracle Database Express Edition (11g) version. It is lightweight and fast.
During the installation, set a password. You will use this password later to log in through the Command Prompt.
After the installation is complete, open Command Prompt and type: sqlplus
Enter the username as system and the password that you created during the installation.
That's it! You are now connected to SQL*Plus.
Start practicing SQL queries on your own.

WHY LINUX IS IMPORTANT FOR DevOps AND SRE ?

THE NOID — Sun, 09 Aug 2026 13:10:08 +0000

FOUNDATION

When people start learning DevOps, they usually jump directly into tools like Docker, Kubernetes, Jenkins, or Terraform.

But there is a skill which much more fundamental behind all of them and that is :

[ LINUX ]

Many beginners see Linux as just another operating system but for DevOps ans SRE, Linux is much more than that.

WHY LINUX MATTER IN DevOps ?

Imagine we are managing a production application and suddenly users start reporting errors.

What will we check first ?

We will connect to the server, look at logs, check resources, analyze processes, and troubleshoot the issue and most of these happen directly on Linux servers.

With commands like :

top            - CPU, RAM usage and running processes
df -h          - Disk space usage
systemctl      - Service status (nginx, apache, etc.)
journalctl     - System and service logs
ps             - Running processes list
free -h        - Memory/RAM usage
uptime         - System uptime and load average

Above commands may look simple, but they are daily tools for engineers keeping system alive.

LINUX IS THE LANGUAGE OF SERVERS

Most cloud workloads run on linux.

Whether it is a virtual machine, a kubernetes node, or a CI/CD runner, Linux is usually working behind the scenes.

Knowing Linux helps you understand :

How applications run.
How service communicate.
How resources are managed.
How failures happens.

AUTOMATION STARTS WITH LINUX

DevOps is all about reducing manual work.

Linux gives engineers powerful tools to automate tasks using :

Bash Scripts
Cron Jobs
Python Scripts
System Configuration Management Tools

LINUX AND CONTAINERS ARE CONNECTED

Modern DevOps depends heavily on containers.

Docker and Kubernetes use Linux concepts like:

Processes
Networking
File System
Resource Limits

Understanding linux makes it easier to understand what happens inside the conatiners instead of just running commands blindly.

LINUX MAKES YOU BETTER AT TROUBLESHOOTING

A good SRE engineer is not someone who only knows tools but knows how system behaves when things break.

It helps you investigate :

High CPU Usage
Memory Problem
Disk Issues
Application Failures
Server Crashes

The ability to find the root cause is one of the most valuable skills in production envirnoment.

WHAT IS LINUX ?

THE NOID — Sun, 09 Aug 2026 13:02:05 +0000

Linux is an open-source operating system [ OS ] based on the Linux Kernel.
It manages computer hardware and software resources, similar to windows and macOS.
It is free, secure, customizable, and widely used by developers and organizations.
It has a massive user base, and used in the world's top 500 most powerful supercomputers.

HISTORY

Linux was created in 1991 by Linus Torvalds as a side project while he was a computer science student.
It was inspired by the UNIX operating system, which was created by Ken Thompson and Dennis Ritchie.
In his first public announcement, Linus described Linux as "Just a hobby, won't be big and professional."
Because it was released as open-source software, more than 16000 developers worldwide have contributed to it since 2005 and this project is still growing with more than 1600 developers for each kernel release.

HOW DOES LINUX WORK ?

User → Application → Kernel → Hardware → Response

Ex: Terminal [ bash ]

Linux works by connecting the user, application, kernel, and hardware together.
The user gives a command in command prompt through an application.
The application sends this request to the Linux Kernel.
The kernel manages system resources and communicates with the hardware.
The hardware performs the task and sends the result back.
Finally, the user can see the required responce.

WHY IS LINUX MORE SECURE THAN WINDOWS ?

Linux is open-source software, it means Linux code is reviewed by thousands of developers.
Strong file permissions and user privileges.
Fewer malware attacks because of its architecture and smaller desktop market share.
Regular security updates from the community.
NOTE : It doesn't mean "It's impossible to hack." It's generally more secure, but any OS can have vulnerabilities.

WHERE IS LINUX USED ?

Servers – Most web servers and cloud systems run on Linux.
Cloud Platforms – Used by AWS, Google Cloud, and other providers.
Supercomputers – Powers many of the world's fastest computers.
Embedded Devices – Used in routers, smart TVs, and IoT devices.
Android – Android uses the Linux Kernel as its foundation.

POPULAR LINUX DISTRIBUTIONS

Ubuntu – Beginner-friendly and widely used for desktops and servers.

Debian – Known for stability and reliability.

Fedora – Provides the latest features and technologies.

Arch Linux – Lightweight and highly customizable.

Red Hat Enterprise Linux (RHEL) – Popular in enterprise and server environments.

Linux Mint – Simple and easy for new Linux users.

KERNEL :

The kernel is the core of an operating system. its acts as a bridge between applications and hardware.

IT MANAGES THINGS LIKE :

CPU
Memory
Processes
Disk
Network
Hardware Devices

EX :

ls

This above command eventually needs the kernel to access the filesystem and retrive information about the files.

FUN FACT ABOUT KERNEL :

Linux is the not whole OS. Linux is the kernel. The rest comes from tools, libraries, applications, and other components.

The kernel talks directly to hardware. Your CPU, RAM, disk, network card, and other devices depend on it.

The kernel is always working in the background. Even when you're doing nothing, it is managing memory, processes, devices, and other resources.

SHELL :

A Shell is a command interpreter. It allows us to communicate with the operating system using commands.

EX :

ls 
cd /var/log 
mkdir test

The shell reads these commands, interprets them, and asks the operating system to perform the required action.

Popular Linux shells include:

Bash
Zsh
Fish
Sh

FUN FACT ABOUT SHELL :

You can actually change your shell without changing the Linux kernel.
You can have multiple shells running at the same time on the same Linux machine.
Shells can do much more than run commands. They can automate entire tasks using scripts.
Bash shell became popular because it was a free, improved version of the older Bourne Shell (sh).