Coding Interview Resources
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This channel contains the free resources and solution of coding problems which are usually asked in the interviews.

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Web Development Interview Questions for Freshers

1. What happens when you type a URL in your browser and press Enter?
Answer:

DNS lookup happens to find the IP address

Browser sends an HTTP/HTTPS request to the server

Server processes and sends back HTML/CSS/JS

Browser renders the page using its rendering engine


2. What is the difference between GET and POST requests?
Answer:

GET: Sends data in the URL, used for fetching data

POST: Sends data in the body, used for submitting data securely


3. What is a responsive website?
Answer:
A responsive website adjusts layout and design based on screen size and device (mobile, tablet, desktop), usually using CSS media queries.

4. What is the role of Webpack in web development?
Answer:
Webpack bundles JavaScript files, CSS, and assets into optimized output for faster website loading and better performance.

5. What is the purpose of async and defer in script tags?
Answer:

async: Loads script asynchronously and executes it immediately

defer: Loads script asynchronously but executes after HTML is parsed


6. What is the difference between localStorage and sessionStorage?
Answer:

localStorage: Stores data with no expiration

sessionStorage: Stores data until the browser tab is closed


7. What is CORS?
Answer:
CORS (Cross-Origin Resource Sharing) is a browser security feature that restricts cross-domain API calls unless the server allows it.

8. What is the difference between null and undefined in JavaScript?
Answer:

undefined: A variable declared but not assigned a value

null: A variable explicitly set to have no value


9. How do you optimize website performance?
Answer:

Minify CSS/JS

Compress images

Use lazy loading

Use caching

Reduce HTTP requests

Use a CDN


10. What is the DOM?
Answer:
DOM (Document Object Model) represents the structure of an HTML document as objects, which JavaScript can interact with to change content dynamically.

Credits: https://whatsapp.com/channel/0029VaiSdWu4NVis9yNEE72z/847
โค1
Web Development Interview Questions Part-2

11. What are semantic HTML elements?
Answer:
Semantic elements clearly describe their meaning in a human- and machine-readable way. Examples: <header>, <footer>, <article>, <nav>.

12. What are HTTP status codes?
Answer:
They indicate the result of an HTTP request.
Common ones:

200 OK (Success)

404 Not Found

500 Internal Server Error

401 Unauthorized

403 Forbidden


13. What is the box model in CSS?
Answer:
The box model includes:

Content

Padding

Border

Margin
It defines how space is taken up around HTML elements.


14. What are pseudo-classes in CSS?
Answer:
Pseudo-classes style elements based on their state.
Examples:

:hover (when mouse is over)

:first-child

:nth-child()


15. How do you make a website SEO-friendly?
Answer:

Use semantic HTML

Add meta tags and alt text

Mobile responsiveness

Fast loading speed

Proper URL structure


16. What is the difference between synchronous and asynchronous in JavaScript?
Answer:

Synchronous: Code runs line by line

Asynchronous: Tasks like API calls don't block other code; use callbacks, promises, or async/await


17. What is a promise in JavaScript?
Answer:
A Promise represents the result of an async operation.
It can be:

Pending

Fulfilled

Rejected


18. What is event bubbling and capturing in JavaScript?
Answer:

Bubbling: Event propagates from child to parent

Capturing: Event goes from parent to child
You can control it using event.stopPropagation()


19. What is a CDN?
Answer:
CDN (Content Delivery Network) delivers static files (images, CSS, JS) via servers closest to the user to improve website speed.

20. What tools do you use for version control?
Answer:
Most common: Git + GitHub
Git tracks changes in code, and GitHub helps you collaborate and manage versions.

Credits: https://whatsapp.com/channel/0029VaiSdWu4NVis9yNEE72z/847
โค5
Complete JavaScript Road Map๐Ÿ”ฅ

A-Z JavaScript๐Ÿ‘‡

1.Variables
โ†ณ var
โ†ณ let
โ†ณ const

2. Data Types
โ†ณ number
โ†ณ string
โ†ณ boolean
โ†ณ null
โ†ณ undefined
โ†ณ symbol

3.Declaring variables
โ†ณ var
โ†ณ let
โ†ณ const

4.Expressions
Primary expressions
โ†ณ this
โ†ณ Literals
โ†ณ []
โ†ณ {}
โ†ณ function
โ†ณ class
โ†ณ function*
โ†ณ async function
โ†ณ async function*
โ†ณ /ab+c/i
โ†ณ string
โ†ณ ( )

Left-hand-side expressions
โ†ณ Property accessors
โ†ณ ?.
โ†ณ new
โ†ณ new .target
โ†ณ import.iss.oneta
โ†ณ super
โ†ณ import()

5.operators
โ†ณ Arithmetic Operators: +, -, *, /, %
โ†ณ Comparison Operators: ==, ===, !=, !==, <, >, <=, >=
โ†ณ Logical Operators: &&, ||, !

6.Control Structures
โ†ณ if
โ†ณ else if
โ†ณ else
โ†ณ switch
โ†ณ case
โ†ณ default

7.Iterations/Loop
โ†ณ do...while
โ†ณ for
โ†ณ for...in
โ†ณ for...of
โ†ณ for await...of
โ†ณ while

8.Functions
โ†ณ Arrow Functions
โ†ณ Default parameters
โ†ณ Rest parameters
โ†ณ arguments
โ†ณ Method definitions
โ†ณ getter
โ†ณ setter

9.Objects and Arrays
โ†ณ Object Literal: { key: value }
โ†ณ Array Literal: [element1, element2, ...]
โ†ณ Object Methods and Properties
โ†ณ Array Methods: push(), pop(), shift(), unshift(),
splice(), slice(), forEach(), map(), filter()

10.Classes and Prototypes
โ†ณ Class Declaration
โ†ณ Constructor Functions
โ†ณ Prototypal Inheritance
โ†ณ extends keyword
โ†ณ super keyword
โ†ณ Private class features
โ†ณ Public class fields
โ†ณ static
โ†ณ Static initialization blocks

11.Error Handling
โ†ณ try,
โ†ณ catch,
โ†ณ finally (exception handling)

ADVANCED CONCEPTS
--------------------------

12.Closures
โ†ณ Lexical Scope
โ†ณ Function Scope
โ†ณ Closure Use Cases

13.Asynchronous JavaScript
โ†ณ Callback Functions
โ†ณ Promises
โ†ณ async/await Syntax
โ†ณ Fetch API
โ†ณ XMLHttpRequest

14.Modules
โ†ณ import and export Statements (ES6 Modules)
โ†ณ CommonJS Modules (require, module.exports)

15.Event Handling
โ†ณ Event Listeners
โ†ณ Event Object
โ†ณ Bubbling and Capturing

16.DOM Manipulation
โ†ณ Selecting DOM Elements
โ†ณ Modifying Element Properties
โ†ณ Creating and Appending Elements

17.Regular Expressions
โ†ณ Pattern Matching
โ†ณ RegExp Methods: test(), exec(), match(), replace()

18.Browser APIs
โ†ณ localStorage and sessionStorage
โ†ณ navigator Object
โ†ณ Geolocation API
โ†ณ Canvas API

19.Web APIs
โ†ณ setTimeout(), setInterval()
โ†ณ XMLHttpRequest
โ†ณ Fetch API
โ†ณ WebSockets

20.Functional Programming
โ†ณ Higher-Order Functions
โ†ณ map(), reduce(), filter()
โ†ณ Pure Functions and Immutability

21.Promises and Asynchronous Patterns
โ†ณ Promise Chaining
โ†ณ Error Handling with Promises
โ†ณ Async/Await

22.ES6+ Features
โ†ณ Template Literals
โ†ณ Destructuring Assignment
โ†ณ Rest and Spread Operators
โ†ณ Arrow Functions
โ†ณ Classes and Inheritance
โ†ณ Default Parameters
โ†ณ let, const Block Scoping

23.Browser Object Model (BOM)
โ†ณ window Object
โ†ณ history Object
โ†ณ location Object
โ†ณ navigator Object

24.Node.js Specific Concepts
โ†ณ require()
โ†ณ Node.js Modules (module.exports)
โ†ณ File System Module (fs)
โ†ณ npm (Node Package Manager)

25.Testing Frameworks
โ†ณ Jasmine
โ†ณ Mocha
โ†ณ Jest

------------------- END-------------------

Some Good Resources To Learn JavaScript
1.Documentation

Mozilla MDN Web Docs
developer.mozilla.org/en-US/docs/Webโ€ฆ
DevDocs
devdocs.io/javascript/

2. Useful Channel's

Javascript Courses: https://t.iss.one/javascript_courses
Programming Resources: https://t.iss.one/programming_guide
FreeCodeCamp: youtube.com/c/FreeCodeCamp

Hope it helps ๐Ÿ˜Š๐ŸŒฑ
โค3
Understanding Python's Slice Function
โค1
๐Ÿ ๐๐ฒ๐ญ๐ก๐จ๐ง ๐Ÿ๐ž๐ฅ๐ญ ๐ข๐ฆ๐ฉ๐จ๐ฌ๐ฌ๐ข๐›๐ฅ๐ž ๐š๐ญ ๐Ÿ๐ข๐ซ๐ฌ๐ญ, ๐›๐ฎ๐ญ ๐ญ๐ก๐ž๐ฌ๐ž ๐Ÿ— ๐ฌ๐ญ๐ž๐ฉ๐ฌ ๐œ๐ก๐š๐ง๐ ๐ž๐ ๐ž๐ฏ๐ž๐ซ๐ฒ๐ญ๐ก๐ข๐ง๐ !
.
.
1๏ธโƒฃ ๐Œ๐š๐ฌ๐ญ๐ž๐ซ๐ž๐ ๐ญ๐ก๐ž ๐๐š๐ฌ๐ข๐œ๐ฌ: Started with foundational Python concepts like variables, loops, functions, and conditional statements.

2๏ธโƒฃ ๐๐ซ๐š๐œ๐ญ๐ข๐œ๐ž๐ ๐„๐š๐ฌ๐ฒ ๐๐ซ๐จ๐›๐ฅ๐ž๐ฆ๐ฌ: Focused on beginner-friendly problems on platforms like LeetCode and HackerRank to build confidence.

3๏ธโƒฃ ๐…๐จ๐ฅ๐ฅ๐จ๐ฐ๐ž๐ ๐๐ฒ๐ญ๐ก๐จ๐ง-๐’๐ฉ๐ž๐œ๐ข๐Ÿ๐ข๐œ ๐๐š๐ญ๐ญ๐ž๐ซ๐ง๐ฌ: Studied essential problem-solving techniques for Python, like list comprehensions, dictionary manipulations, and lambda functions.

4๏ธโƒฃ ๐‹๐ž๐š๐ซ๐ง๐ž๐ ๐Š๐ž๐ฒ ๐‹๐ข๐›๐ซ๐š๐ซ๐ข๐ž๐ฌ: Explored popular libraries like Pandas, NumPy, and Matplotlib for data manipulation, analysis, and visualization.

5๏ธโƒฃ ๐…๐จ๐œ๐ฎ๐ฌ๐ž๐ ๐จ๐ง ๐๐ซ๐จ๐ฃ๐ž๐œ๐ญ๐ฌ: Built small projects like a to-do app, calculator, or data visualization dashboard to apply concepts.

6๏ธโƒฃ ๐–๐š๐ญ๐œ๐ก๐ž๐ ๐“๐ฎ๐ญ๐จ๐ซ๐ข๐š๐ฅ๐ฌ: Followed creators like CodeWithHarry and Shradha Khapra for in-depth Python tutorials.

7๏ธโƒฃ ๐ƒ๐ž๐›๐ฎ๐ ๐ ๐ž๐ ๐‘๐ž๐ ๐ฎ๐ฅ๐š๐ซ๐ฅ๐ฒ: Made it a habit to debug and analyze code to understand errors and optimize solutions.

8๏ธโƒฃ ๐‰๐จ๐ข๐ง๐ž๐ ๐Œ๐จ๐œ๐ค ๐‚๐จ๐๐ข๐ง๐  ๐‚๐ก๐š๐ฅ๐ฅ๐ž๐ง๐ ๐ž๐ฌ: Participated in coding challenges to simulate real-world problem-solving scenarios.

9๏ธโƒฃ ๐’๐ญ๐š๐ฒ๐ž๐ ๐‚๐จ๐ง๐ฌ๐ข๐ฌ๐ญ๐ž๐ง๐ญ: Practiced daily, worked on diverse problems, and never skipped Python for more than a day.

I have curated the best interview resources to crack Python Interviews ๐Ÿ‘‡๐Ÿ‘‡
https://whatsapp.com/channel/0029VaiM08SDuMRaGKd9Wv0L

Hope you'll like it

Like this post if you need more resources like this ๐Ÿ‘โค๏ธ

#Python
โค3
Top Libraries & Frameworks by Language ๐Ÿ“š๐Ÿ’ป

โฏ Python
โ€ƒโ€ข Pandas โžŸ Data Analysis
โ€ƒโ€ข NumPy โžŸ Math & Arrays
โ€ƒโ€ข Scikit-learn โžŸ Machine Learning
โ€ƒโ€ข TensorFlow / PyTorch โžŸ Deep Learning
โ€ƒโ€ข Flask / Django โžŸ Web Development
โ€ƒโ€ข OpenCV โžŸ Image Processing

โฏ JavaScript / TypeScript
โ€ƒโ€ข React โžŸ UI Development
โ€ƒโ€ข Vue โžŸ Lightweight SPAs
โ€ƒโ€ข Angular โžŸ Enterprise Apps
โ€ƒโ€ข Next.js โžŸ Full-Stack Web
โ€ƒโ€ข Express โžŸ Backend APIs
โ€ƒโ€ข Three.js โžŸ 3D Web Graphics

โฏ Java
โ€ƒโ€ข Spring Boot โžŸ Microservices
โ€ƒโ€ข Hibernate โžŸ ORM
โ€ƒโ€ข Apache Maven โžŸ Build Automation
โ€ƒโ€ข Apache Kafka โžŸ Real-Time Data

โฏ C++
โ€ƒโ€ข Boost โžŸ Utility Libraries
โ€ƒโ€ข Qt โžŸ GUI Applications
โ€ƒโ€ข Unreal Engine โžŸ Game Development

โฏ C#
โ€ƒโ€ข .NET / ASP.NET โžŸ Web Apps
โ€ƒโ€ข Unity โžŸ Game Development
โ€ƒโ€ข Entity Framework โžŸ ORM

โฏ R
โ€ƒโ€ข ggplot2 โžŸ Data Visualization
โ€ƒโ€ข dplyr โžŸ Data Manipulation
โ€ƒโ€ข caret โžŸ Machine Learning
โ€ƒโ€ข Shiny โžŸ Interactive Dashboards

โฏ PHP
โ€ƒโ€ข Laravel โžŸ Full-Stack Web
โ€ƒโ€ข Symfony โžŸ Web Framework
โ€ƒโ€ข PHPUnit โžŸ Testing

โฏ Go (Golang)
โ€ƒโ€ข Gin โžŸ Web Framework
โ€ƒโ€ข Gorilla โžŸ Web Toolkit
โ€ƒโ€ข GORM โžŸ ORM for Go

โฏ Rust
โ€ƒโ€ข Actix โžŸ Web Framework
โ€ƒโ€ข Rocket โžŸ Web Development
โ€ƒโ€ข Tokio โžŸ Async Runtime

Coding Resources: https://whatsapp.com/channel/0029VahiFZQ4o7qN54LTzB17

React with โค๏ธ for more useful content
โค2
9 ESSENTIAL MACHINE LEARNING ALGORITHMS
โค3
Machine Learning Roadmap
โค2
12 MPC Servers you can use in 2025
โค1
Interviewer: You have 2 minutes. Explain the JavaScript Event Loop to me.

My answer: Challenge accepted, letโ€™s go!

โžค Single-Threaded Execution:
JavaScript is single-threaded, which means it can only execute one task at a time. This is managed by the call stack, where functions are executed one by one.

โžค Call Stack: Think of the call stack as a stack of plates. Every time a function is called, a new plate (function) is added to the stack. When the function finishes, the plate is removed from the stack.

โžค Web APIs: For asynchronous operations like setTimeout, DOM events, and HTTP requests, JavaScript relies on Web APIs provided by the browser. These operations are handled outside of the call stack.

โžค Callback Queue: When an asynchronous operation completes, its callback is placed in the callback queue. This queue waits until the call stack is clear before pushing the next callback onto the stack.

โžค Event Loop: The event loop is like a manager that constantly checks if the call stack is empty. When it is, the event loop takes the first callback from the callback queue and adds it to the call stack.

โžค Microtasks Queue: There's also a microtasks queue for tasks like promises. This queue has higher priority than the callback queue. The event loop checks the microtasks queue first, ensuring these tasks are processed before other callbacks.

โžค Priority Handling: To sum it up, the event loop first checks the microtasks queue. If it's empty, it moves to the callback queue. This ensures that critical tasks, like promises, are handled promptly.

Thatโ€™s the JavaScript Event Loop.

Timeโ€™s up..
โค8
Starting with coding is a fantastic foundation for a tech career. As you grow your skills, you might explore various areas depending on your interests and goals:

โ€ข Web Development: If you enjoy building websites and web applications, diving into web development could be your next step. You can specialize in front-end (HTML, CSS, JavaScript) or back-end (Python, Java, Node.js) development, or become a full-stack developer.

โ€ข Mobile App Development: If you're excited about creating apps for smartphones and tablets, you might explore mobile development. Learn Swift for iOS or Kotlin for Android, or use cross-platform tools like Flutter or React Native.

โ€ข Data Science and Analysis: If analyzing and interpreting data intrigues you, focusing on data science or data analysis could be your path. You'll use languages like Python or R and tools like Pandas, NumPy, and SQL.

โ€ข Game Development: If youโ€™re passionate about creating games, you might explore game development. Languages like C# with Unity or C++ with Unreal Engine are popular choices in this field.

โ€ข Cybersecurity: If you're interested in protecting systems from threats, diving into cybersecurity could be a great fit. Learn about ethical hacking, penetration testing, and security protocols.

โ€ข Software Engineering: If you enjoy designing and building complex software systems, focusing on software engineering might be your calling. This involves writing code, but also planning, testing, and maintaining software.

โ€ข Automation and Scripting: If you're interested in making repetitive tasks easier, scripting and automation could be a good path. Python, Bash, and PowerShell are popular for writing scripts to automate tasks.

โ€ข Artificial Intelligence and Machine Learning: If you're fascinated by creating systems that learn and adapt, exploring AI and machine learning could be your next step. Youโ€™ll work with algorithms, data, and models to create intelligent systems.

Regardless of the path you choose, the key is to keep coding, learning, and challenging yourself with new projects. Each step forward will deepen your understanding and open new opportunities in the tech world.
โค6
*You can learn ReactJS easily ๐Ÿคฉ*

Here's all you need to get started ๐Ÿ™Œ

1.Components
โ€ข Functional Components
โ€ข Class Components
โ€ข JSX (JavaScript XML) Syntax

2.Props (Properties)
โ€ข Passing Props
โ€ข Default Props
โ€ข Prop Types

3.State
โ€ข useState Hook
โ€ข Class Component State
โ€ข Immutable State

4.Lifecycle Methods (Class Components)
โ€ข componentDidMount
โ€ข componentDidUpdate
โ€ข componentWillUnmount

5.Hooks (Functional Components)
โ€ข useState
โ€ข useEffect
โ€ข useContext
โ€ข useReducer
โ€ข useCallback
โ€ข useMemo
โ€ข useRef
โ€ข useImperativeHandle
โ€ข useLayoutEffect

6.Event Handling
โ€ข Handling Events in Functional Components
โ€ข Handling Events in Class Components

7.Conditional Rendering
โ€ข if Statements
โ€ข Ternary Operators
โ€ข Logical && Operator

8.Lists and Keys
โ€ข Rendering Lists
โ€ข Keys in React Lists

9.Component Composition
โ€ข Reusing Components
โ€ข Children Props
โ€ข Composition vs Inheritance

10.Higher-Order Components (HOC)
โ€ข Creating HOCs
โ€ข Using HOCs for Reusability

11.Render Props
โ€ข Using Render Props Pattern

12.React Router
โ€ข <BrowserRouter>
โ€ข <Route>
โ€ข <Link>
โ€ข <Switch>
โ€ข Route Parameters

13.Navigation
โ€ข useHistory Hook
โ€ข useLocation Hook

State Management

14.Context API
โ€ข Creating Context
โ€ข useContext Hook

15.Redux
โ€ข Actions
โ€ข Reducers
โ€ข Store
โ€ข connect Function (React-Redux)

16.Forms
โ€ข Handling Form Data
โ€ข Controlled Components
โ€ข Uncontrolled Components

17.Side Effects
โ€ข useEffect for Data Fetching
โ€ข useEffect Cleanup

18.AJAX Requests
โ€ข Fetch API
โ€ข Axios Library

Error Handling

19.Error Boundaries
โ€ข componentDidCatch (Class Components)
โ€ข ErrorBoundary Component (Functional
Components)

20.Testing
โ€ข Jest Testing Framework
โ€ข React Testing Library

21. Best Practices
โ€ข Code Splitting
โ€ข PureComponent and React.iss.onemo
โ€ข Avoiding Reconciliation
โ€ข Keys for Dynamic Lists

22.Optimization
โ€ข Memoization
โ€ข Profiling and Performance Monitoring

23. Build and Deployment
โ€ข Create React App (CRA)
โ€ข Production Builds
โ€ข Deployment Strategies

Frameworks and Libraries

24.Styling Libraries
โ€ข Styled-components
โ€ข CSS Modules

25.State Management Libraries
โ€ข Redux
โ€ข MobX

26.Routing Libraries
โ€ข React Router
โ€ข Reach Router
โค2
Typical C++ interview questions sorted by experience

Junior:
- What are the key features of object-oriented programming in C++?
- Explain the differences between public, private, and protected access specifiers in C++.
- Distinguish between function overloading and overriding in C++.
- Compare and contrast abstract classes and interfaces in C++.
- Can an interface inherit from another interface in C++?
- Define the static keyword in C++ and its significance.
- Is it possible to override a static method in C++?
- Explain the concepts of polymorphism and inheritance in C++.
- Can constructors be inherited in C++?
- Discuss pass-by-reference and pass-by-value for objects in C++.
- Compare == and .equals for string comparison in C++.
- Explain the purposes of the hashCode() and equals() functions.
- What does the Serializable interface do? How is it related to Parcelable in Android?
- Differentiate between Array and ArrayList in C++. When would you use each?
- Explain the distinction between Integer and int in C++.
- Define ThreadPool and discuss its advantages over using simple threads.
- Differentiate between local, instance, and class variables in C++.

Mid:
- What is reflection in C++?
- Define dependency injection and name a few libraries. Have you used any?
- Explain strong, soft, and weak references in C++.
- Interpret the meaning of the synchronized keyword.
- Can memory leaks occur in C++?
- Is it necessary to set references to null in C++?
- Why is a String considered immutable?
- Discuss transient and volatile modifiers in C++.
- What is the purpose of the finalize() method?
- How does the try{} finally{} block work in C++?
- Explain the difference between object instantiation and initialization.
- Under what conditions is a static block executed in C++?
- Why are generics used in C++?
- Mention some design patterns you are familiar with. Which do you typically use?
- Name some types of testing methodologies in C++.

Senior:
- Explain how std::stoi (string to integer) works in C++.
- What is the "double-check locking" problem, and how can it be solved in C++?
- Differentiate between StringBuffer and StringBuilder in C++.
- How is StringBuilder implemented to avoid the immutable string allocation problem?
- Explain the purpose of the Class.forName method in C++.
- Define Autoboxing and Unboxing in C++.
- What's the difference between Enumeration and Iterator in C++?
- Explain the difference between fail-fast and fail-safe in C++.
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Top linked list questions to practice:

1. ๐Ÿ”„ Reverse a Linked List

2. ๐Ÿ” Detect a Cycle in a Linked List

3. ๐Ÿค Find the Merge Point of Two Linked Lists

4. ๐Ÿšซ Remove N-th Node From End of List

5. ๐Ÿ”— Merge Two Sorted Linked Lists

6. ๐Ÿ–ผ๏ธ Check if a Linked List is a Palindrome

7. ๐Ÿšจ Remove Duplicates from a Sorted List

8. ๐ŸŽฏ Find the Middle of a Linked List

9. ๐Ÿ”„ Rotate a Linked List

10. ๐Ÿ“‘ Implement a Doubly Linked List

11. ๐Ÿ“Š Implement a Circular Linked List

12. ๐Ÿ› ๏ธ Add Two Numbers Represented by Linked Lists

13. ๐Ÿงน Remove Linked List Elements

14. ๐Ÿงฉ Partition List around a value

15. ๐Ÿ”„ Reverse Nodes in k-Group
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1. Does SQL support programming language features?
It is true that SQL is a language, but it does not support programming as it is not a programming language, it is a command language. We do not have some programming concepts in SQL like for loops or while loop, we only have commands which we can use to query, update, delete, etc. data in the database. SQL allows us to manipulate data in a database.

2. What is a trigger?
Trigger is a statement that a system executes automatically when there is any modification to the database. In a trigger, we first specify when the trigger is to be executed and then the action to be performed when the trigger executes. Triggers are used to specify certain integrity constraints and referential constraints that cannot be specified using the constraint mechanism of SQL.

3. What are aggregate and scalar functions?
For doing operations on data SQL has many built-in functions, they are categorized into two categories and further sub-categorized into seven different functions under each category. The categories are:
Aggregate functions:
These functions are used to do operations from the values of the column and a single value is returned.
Scalar functions:
These functions are based on user input, these too return a single value.

4. Define SQL Order by the statement?
The ORDER BY statement in SQL is used to sort the fetched data in either ascending or descending according to one or more columns.
By default ORDER BY sorts the data in ascending order.
We can use the keyword DESC to sort the data in descending order and the keyword ASC to sort in ascending order.

5. What is the difference between primary key and unique constraints? 
The primary key cannot have NULL values, the unique constraints can have NULL values. There is only one primary key in a table, but there can be multiple unique constraints. The primary key creates the clustered index automatically but the unique key does not.
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SQL (Structured Query Language) is a standard programming language used to manage and manipulate relational databases. Here are some key concepts to understand the basics of SQL:

1. Database: A database is a structured collection of data organized in tables, which consist of rows and columns.

2. Table: A table is a collection of related data organized in rows and columns. Each row represents a record, and each column represents a specific attribute or field.

3. Query: A SQL query is a request for data or information from a database. Queries are used to retrieve, insert, update, or delete data in a database.

4. CRUD Operations: CRUD stands for Create, Read, Update, and Delete. These are the basic operations performed on data in a database using SQL:
   - Create (INSERT): Adds new records to a table.
   - Read (SELECT): Retrieves data from one or more tables.
   - Update (UPDATE): Modifies existing records in a table.
   - Delete (DELETE): Removes records from a table.

5. Data Types: SQL supports various data types to define the type of data that can be stored in each column of a table, such as integer, text, date, and decimal.

6. Constraints: Constraints are rules enforced on data columns to ensure data integrity and consistency. Common constraints include:
   - Primary Key: Uniquely identifies each record in a table.
   - Foreign Key: Establishes a relationship between two tables.
   - Unique: Ensures that all values in a column are unique.
   - Not Null: Specifies that a column cannot contain NULL values.

7. Joins: Joins are used to combine rows from two or more tables based on a related column between them. Common types of joins include INNER JOIN, LEFT JOIN (or LEFT OUTER JOIN), RIGHT JOIN (or RIGHT OUTER JOIN), and FULL JOIN (or FULL OUTER JOIN).

8. Aggregate Functions: SQL provides aggregate functions to perform calculations on sets of values. Common aggregate functions include SUM, AVG, COUNT, MIN, and MAX.

9. Group By: The GROUP BY clause is used to group rows that have the same values into summary rows. It is often used with aggregate functions to perform calculations on grouped data.

10. Order By: The ORDER BY clause is used to sort the result set of a query based on one or more columns in ascending or descending order.

Understanding these basic concepts of SQL will help you write queries to interact with databases effectively. Practice writing SQL queries and experimenting with different commands to become proficient in using SQL for database management and manipulation.

SQL Learning Series: https://whatsapp.com/channel/0029VanC5rODzgT6TiTGoa1v/1075
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