Harvard University offers a ton of FREE online courses.
From Computer Science to Artificial Intelligence.
Here are 10 FREE courses you don't want to miss

1. Introduction to Computer Science
An introduction to the intellectual enterprises of computer science and the art of programming.
Check here 👇
https://pll.harvard.edu/course/cs50-introduction-computer-science?delta=0


2. Web Programming with Python and JavaScript
This course takes you deeply into the design and implementation of web apps with Python, JavaScript, and SQL using frameworks like Django, React, and Bootstrap.
Check here 👇
https://pll.harvard.edu/course/cs50s-web-programming-python-and-javascript?delta=0

3. Introduction to Programming with Scratch

A gentle introduction to programming that prepares you for subsequent courses in coding.
Check here 👇
https://pll.harvard.edu/course/cs50s-introduction-programming-scratch?delta=0

4. Introduction to Programming with Python
An introduction to programming using Python, a popular language for general-purpose programming, data science, web programming, and more.
Check here 👇
https://edx.org/course/cs50s-introduction-to-programming-with-python



5. Understanding Technology
This is CS50’s introduction to technology for students who don’t (yet!) consider themselves computer persons.
Check here 👇
https://pll.harvard.edu/course/cs50s-understanding-technology-0?delta=0

6. Introduction to Artificial Intelligence with Python
Learn to use machine learning in Python in this introductory course on artificial intelligence.
Check here 👇
https://pll.harvard.edu/course/cs50s-introduction-artificial-intelligence-python?delta=0


7. Introduction to Game Development
Learn about the development of 2D and 3D interactive games in this hands-on course, as you explore the design of games such as Super Mario Bros., Pokémon, Angry Birds, and more.
Check here 👇
https://pll.harvard.edu/course/cs50s-introduction-game-development?delta=0

8. CS50's Computer Science for Business Professionals
This is CS50’s introduction to computer science for business professionals.
Check here 👇
https://pll.harvard.edu/course/cs50s-computer-science-business-professionals-0?delta=0


9. Mobile App Development with React Native
Learn about mobile app development with React Native, a popular framework maintained by Facebook that enables cross-platform native apps using JavaScript without Java or Swift.
Check here 👇
https://pll.harvard.edu/course/cs50s-mobile-app-development-react-native?delta=0

10. Introduction to Data Science with Python
Join Harvard University instructor Pavlos Protopapas in this online course to learn how to use Python to harness and analyze data.
Check here 👇
https://pll.harvard.edu/course/introduction-data-science-python?delta=0

𝐈𝐁𝐌 𝐅𝐑𝐄𝐄 𝐂𝐞𝐫𝐭𝐢𝐟𝐢𝐜𝐚𝐭𝐢𝐨𝐧 𝐂𝐨𝐮𝐫𝐬𝐞𝐬😍

🚀 Dive into the world of Data Analytics with these 6 free courses by IBM!

Gain practical knowledge and stand out in your career with tools designed for real-world applications.

All courses come with expert guidance and are free to access!🎉

𝐋𝐢𝐧𝐤 👇:- 
 
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🔟 Data Analyst Project Ideas for Beginners

1. Sales Analysis Dashboard: Use tools like Excel or Tableau to create a dashboard analyzing sales data. Visualize trends, top products, and seasonal patterns.

2. Customer Segmentation: Analyze customer data using clustering techniques (like K-means) to segment customers based on purchasing behavior and demographics.

3. Social Media Metrics Analysis: Gather data from social media platforms to analyze engagement metrics. Create visualizations to highlight trends and performance.

4. Survey Data Analysis: Conduct a survey and analyze the results using statistical techniques. Present findings with visualizations to showcase insights.

5. Exploratory Data Analysis (EDA): Choose a public dataset and perform EDA using Python (Pandas, Matplotlib) or R (tidyverse). Summarize key insights and visualizations.

6. Employee Performance Analysis: Analyze employee performance data to identify trends in productivity, turnover rates, and training effectiveness.

7. Public Health Data Analysis: Use datasets from public health sources (like CDC) to analyze trends in health metrics (e.g., vaccination rates, disease outbreaks) and visualize findings.

8. Real Estate Market Analysis: Analyze real estate listings to find trends in pricing, location, and features. Use data visualization to present your findings.

9. Weather Data Visualization: Collect weather data and analyze trends over time. Create visualizations to show changes in temperature, precipitation, or extreme weather events.

10. Financial Analysis: Analyze a company’s financial statements to assess its performance over time. Create visualizations to highlight key financial ratios and trends.

Data Analytics Resources 👇👇
https://whatsapp.com/channel/0029VaGgzAk72WTmQFERKh02

Hope it helps :)

If I were to start Data Analytics in 2025 💫🚀

❯ Python
https://cs50.harvard.edu/python/2022/

https://www.freecodecamp.org/learn/data-analysis-with-python/

https://t.iss.one/pythonanalyst

❯ SQL
https://online.stanford.edu/courses/soe-ydatabases0005-databases-relational-databases-and-sql

https://www.freecodecamp.org/learn/relational-database/

https://bit.ly/3YpMM2y

❯ Excel
https://excel-practice-online.com/

https://t.iss.one/excel_analyst

❯ Power BI
https://www.freecodecamp.org/learn/data-visualization/

https://t.iss.one/PowerBI_analyst

https://www.workout-wednesday.com/power-bi-challenges/

❯ Tableau
https://www.tableau.com/learn/training

❯ Jobs
https://t.iss.one/jobs_SQL

https://t.iss.one/jobinterviewsprep

https://t.iss.one/datasciencej

❯ Mathematics (incl. Statistics)
ocw.mit.edu/search/?d=Mathematics&s=department_course_numbers.sort_coursenum

https://www.sherrytowers.com/cowan_statistical_data_analysis.pdf

❯ Data Science
cognitiveclass.ai/courses/data-science-101

https://kaggle.com/learn

https://t.iss.one/datasciencefun/290

❯ Machine Learning
https://developers.google.com/machine-learning/crash-course

https://www.freecodecamp.org/learn/machine-learning-with-python/

❯ Artificial Intelligence
https://imp.i115008.net/qn27PL

introtodeeplearning.com

t.iss.one/machinelearning_deeplearning/

t.iss.one/aifoundations

❯ Data Engineering
https://bit.ly/3fGRjLu

https://t.iss.one/sql_engineer

Join @free4unow_backup for more free resources

Like for more ❤️

ENJOY LEARNING👍👍

7 Useful Python One-Liners

1. Reverse a string

print("Python"[::-1]) # Output: nohtyP

2. Check for Palindrome

is_palindrome = lambda s: s == s[::-1]
print(is_palindrome("madam")) # Output: True

3. Get all even numbers from a list

print([x for x in range(20) if x % 2 == 0])

4. Flatten a nested list

print([item for sublist in [[1,2],[3,4]] for item in sublist])

5. Find factorial of a number

import math; print(math.factorial(5)) # Output: 120

6. Count frequency of elements

from collections import Counter
print(Counter("banana")) # Output: {'a': 3, 'b': 1, 'n': 2}

7. Swap two variables

a, b = 5, 10
a, b = b, a
print(a, b) # Output: 10 5

For all resources and cheat sheets, check out my Telegram channel: https://t.iss.one/pythonproz

Python Projects: https://whatsapp.com/channel/0029Vau5fZECsU9HJFLacm2a

Latest Jobs & Internship Opportunities: https://whatsapp.com/channel/0029VaI5CV93AzNUiZ5Tt226

Hope it helps :)

If you're serious about getting into Data Science with Python, follow this 5-step roadmap.

Each phase builds on the previous one, so don’t rush.

Take your time, build projects, and keep moving forward.

Step 1: Python Fundamentals
Before anything else, get your hands dirty with core Python.
This is the language that powers everything else.

✅ What to learn:
type(), int(), float(), str(), list(), dict()
if, elif, else, for, while, range()
def, return, function arguments
List comprehensions: [x for x in list if condition]
– Mini Checkpoint:
Build a mini console-based data calculator (inputs, basic operations, conditionals, loops).

Step 2: Data Cleaning with Pandas
Pandas is the tool you'll use to clean, reshape, and explore data in real-world scenarios.

✅ What to learn:
Cleaning: df.dropna(), df.fillna(), df.replace(), df.drop_duplicates()
Merging & reshaping: pd.merge(), df.pivot(), df.melt()
Grouping & aggregation: df.groupby(), df.agg()
– Mini Checkpoint:
Build a data cleaning script for a messy CSV file. Add comments to explain every step.

Step 3: Data Visualization with Matplotlib
Nobody wants raw tables.
Learn to tell stories through charts.

✅ What to learn:
Basic charts: plt.plot(), plt.scatter()
Advanced plots: plt.hist(), plt.kde(), plt.boxplot()
Subplots & customizations: plt.subplots(), fig.add_subplot(), plt.title(), plt.legend(), plt.xlabel()
– Mini Checkpoint:
Create a dashboard-style notebook visualizing a dataset, include at least 4 types of plots.

Step 4: Exploratory Data Analysis (EDA)
This is where your analytical skills kick in.
You’ll draw insights, detect trends, and prepare for modeling.

✅ What to learn:
Descriptive stats: df.mean(), df.median(), df.mode(), df.std(), df.var(), df.min(), df.max(), df.quantile()
Correlation analysis: df.corr(), plt.imshow(), scipy.stats.pearsonr()
— Mini Checkpoint:
Write an EDA report (Markdown or PDF) based on your findings from a public dataset.

Step 5: Intro to Machine Learning with Scikit-Learn
Now that your data skills are sharp, it's time to model and predict.

✅ What to learn:
Training & evaluation: train_test_split(), .fit(), .predict(), cross_val_score()
Regression: LinearRegression(), mean_squared_error(), r2_score()
Classification: LogisticRegression(), accuracy_score(), confusion_matrix()
Clustering: KMeans(), silhouette_score()

– Final Checkpoint:

Build your first ML project end-to-end
✅ Load data
✅ Clean it
✅ Visualize it
✅ Run EDA
✅ Train & test a model
✅ Share the project with visuals and explanations on GitHub

Don’t just complete tutorialsm create things.

Explain your work.
Build your GitHub.
Write a blog.

That’s how you go from “learning” to “landing a job

Best Data Science & Machine Learning Resources: https://topmate.io/coding/914624

All the best 👍👍

Who is Data Scientist?

He/she is responsible for collecting, analyzing and interpreting the results, through a large amount of data. This process is used to take an important decision for the business, which can affect the growth and help to face compititon in the market.

A data scientist analyzes data to extract actionable insight from it. More specifically, a data scientist:

Determines correct datasets and variables.

Identifies the most challenging data-analytics problems.

Collects large sets of data- structured and unstructured, from different sources.

Cleans and validates data ensuring accuracy, completeness, and uniformity.

Builds and applies models and algorithms to mine stores of big data.

Analyzes data to recognize patterns and trends.

Interprets data to find solutions.

Communicates findings to stakeholders using tools like visualization.

AI Side Hustles Cheat Sheet 💵

This cheat sheet is a quick reference guide designed to help you implement key strategies for
launching profitable AI side hustles. Whether it's creating content, selling products, or offering
services, AI tools make it easier to start generating income.

1. Why Now is the Best Time to Start an AI Side Hustle
- Since the release of ChatGPT in November 2022, AI has grown significantly across many
industries.
- AI tools can save time and effort, helping you launch side hustles quickly.
- Identify the best AI-powered side hustle for your goals and take action.

2. Create a Faceless YouTube Channel using AI Tools
- Benefits: A faceless YouTube channel allows you to create content without being on camera.
- Use ChatGPT to identify profitable niches for your channel.
- Create visuals and branding with AI tools like MidJourney or Canva AI.
- Use ChatGPT to brainstorm video topics and generate scripts.
- Use tools like InVideo.io to create videos from your scripts.
- Optimize your videos for YouTube SEO and promote them on social media.

3. Create a Profitable Online Course with AI Tools
- Use ChatGPT to find high-demand niches and sub-niches.
- Use ChatGPT to develop course outlines and video scripts.
- Create course videos using AI tools like elai.io.
- Select a platform (e.g., Teachable, Udemy) to launch and promote your course.

4. Sell Profitable Etsy Printables Created with AI Tools
- There is a growing demand for digital printables like planners, clipart, and wedding stationery
on Etsy.
- Conduct market research to identify profitable printable categories.
- Use AI tools like MidJourney or Canva to create unique designs.
- Use ChatGPT to generate new product ideas and optimize product descriptions.
- Set up and optimize your Etsy shop for visibility and sales.

5. Publish Children's Story Books with AI Tools on Amazon
- Children's storybooks are in demand on Amazon.
- Research popular genres and trends using Amazon KDP.
- Use ChatGPT to generate story ideas and develop narratives.
- Create illustrations using AI art tools.
- Format and upload your book to Amazon KDP, then optimize and promote it.

6. Leverage AI Tools for Profitable Affiliate Marketing
- Research and select profitable affiliate offers to promote.
- Use ChatGPT to create content for PDFs or blogs that promote your offer.
- Design engaging materials with Canva.
- Find the best platforms for distributing your affiliate marketing content, and optimize listings for
better conversions.

7. Offer Copywriting Services with AI Assistance
- Offer services such as product descriptions, email campaigns, and ad copy creation using AI
tools.
- Use ChatGPT to generate high-converting copy quickly and efficiently.
- Promote your copywriting services on platforms like Fiverr, Upwork, or freelancing websites.

Data Science Interview Questions with Answers

1. Can you explain how the memory cell in an LSTM is implemented computationally?

The memory cell in an LSTM is implemented as a forget gate, an input gate, and an output gate. The forget gate controls how much information from the previous cell state is forgotten. The input gate controls how much new information from the current input is allowed into the cell state. The output gate controls how much information from the cell state is allowed to pass out to the next cell state.


2. What is CTE in SQL?

A CTE (Common Table Expression) is a one-time result set that only exists for the duration of the query. It allows us to refer to data within a single SELECT, INSERT, UPDATE, DELETE, CREATE VIEW, or MERGE statement's execution scope. It is temporary because its result cannot be stored anywhere and will be lost as soon as a query's execution is completed.


3. List the advantages NumPy Arrays have over Python lists?

Python’s lists, even though hugely efficient containers capable of a number of functions, have several limitations when compared to NumPy arrays. It is not possible to perform vectorised operations which includes element-wise addition and multiplication. They also require that Python store the type information of every element since they support objects of different types. This means a type dispatching code must be executed each time an operation on an element is done.

4. What’s the F1 score? How would you use it?

The F1 score is a measure of a model’s performance. It is a weighted average of the precision and recall of a model, with results tending to 1 being the best, and those tending to 0 being the worst.

5. Name an example where ensemble techniques might be useful?

Ensemble techniques use a combination of learning algorithms to optimize better predictive performance. They typically reduce overfitting in models and make the model more robust (unlikely to be influenced by small changes in the training data). You could list some examples of ensemble methods (bagging, boosting, the “bucket of models” method) and demonstrate how they could increase predictive power.

Data Science Resources: https://whatsapp.com/channel/0029Va8v3eo1NCrQfGMseL2D

Hey guys!

I’ve been getting a lot of requests from you all asking for solid Data Analytics projects that can help you boost resume and build real skills.

So here you go —

These aren’t just “for practice,” they’re portfolio-worthy projects that show recruiters you’re ready for real-world work.

1. Sales Performance Dashboard

Tools: Excel / Power BI / Tableau
You’ll take raw sales data and turn it into a clean, interactive dashboard. Show key metrics like revenue, profit, top products, and regional trends.
Skills you build: Data cleaning, slicing & filtering, dashboard creation, business storytelling.

2. Customer Churn Analysis

Tools: Python (Pandas, Seaborn)

Work with a telecom or SaaS dataset to identify which customers are likely to leave and why.

Skills you build: Exploratory data analysis, visualization, correlation, and basic machine learning.


3. E-commerce Product Insights using SQL

Tools: SQL + Power BI

Analyze product categories, top-selling items, and revenue trends from a sample e-commerce dataset.

Skills you build: Joins, GROUP BY, aggregation, data modeling, and visual storytelling.


4. HR Analytics Dashboard

Tools: Excel / Power BI

Dive into employee data to find patterns in attrition, hiring trends, average salaries by department, etc.

Skills you build: Data summarization, calculated fields, visual formatting, DAX basics.


5. Movie Trends Analysis (Netflix or IMDb Dataset)

Tools: Python (Pandas, Matplotlib)

Explore trends across genres, ratings, and release years. Great for people who love entertainment and want to show creativity.

Skills you build: Data wrangling, time-series plots, filtering techniques.


6. Marketing Campaign Analysis

Tools: Excel / Power BI / SQL

Analyze data from a marketing campaign to measure ROI, conversion rates, and customer engagement. Identify which channels or strategies worked best and suggest improvements.

Skills you build: Data blending, KPI calculation, segmentation, and actionable insights.


7. Financial Expense Analysis & Budget Forecasting

Tools: Excel / Power BI / Python

Work on a company’s expense data to analyze spending patterns, categorize expenses, and create a forecasting model to predict future budgets.

Skills you build: Time series analysis, forecasting, budgeting, and financial storytelling.


Pick 2–3 projects. Don’t just show the final visuals — explain your process on LinkedIn or GitHub. That’s what sets you apart.

Like for more useful content ❤️

If I Were to Start My Data Science Career from Scratch, Here's What I Would Do 👇

1️⃣ Master Advanced SQL

Foundations: Learn database structures, tables, and relationships.

Basic SQL Commands: SELECT, FROM, WHERE, ORDER BY.

Aggregations: Get hands-on with SUM, COUNT, AVG, MIN, MAX, GROUP BY, and HAVING.

JOINs: Understand LEFT, RIGHT, INNER, OUTER, and CARTESIAN joins.

Advanced Concepts: CTEs, window functions, and query optimization.

Metric Development: Build and report metrics effectively.


2️⃣ Study Statistics & A/B Testing

Descriptive Statistics: Know your mean, median, mode, and standard deviation.

Distributions: Familiarize yourself with normal, Bernoulli, binomial, exponential, and uniform distributions.

Probability: Understand basic probability and Bayes' theorem.

Intro to ML: Start with linear regression, decision trees, and K-means clustering.

Experimentation Basics: T-tests, Z-tests, Type 1 & Type 2 errors.

A/B Testing: Design experiments—hypothesis formation, sample size calculation, and sample biases.


3️⃣ Learn Python for Data

Data Manipulation: Use pandas for data cleaning and manipulation.

Data Visualization: Explore matplotlib and seaborn for creating visualizations.

Hypothesis Testing: Dive into scipy for statistical testing.

Basic Modeling: Practice building models with scikit-learn.


4️⃣ Develop Product Sense

Product Management Basics: Manage projects and understand the product life cycle.

Data-Driven Strategy: Leverage data to inform decisions and measure success.

Metrics in Business: Define and evaluate metrics that matter to the business.


5️⃣ Hone Soft Skills

Communication: Clearly explain data findings to technical and non-technical audiences.

Collaboration: Work effectively in teams.

Time Management: Prioritize and manage projects efficiently.

Self-Reflection: Regularly assess and improve your skills.


6️⃣ Bonus: Basic Data Engineering

Data Modeling: Understand dimensional modeling and trade-offs in normalization vs. denormalization.

ETL: Set up extraction jobs, manage dependencies, clean and validate data.

Pipeline Testing: Conduct unit testing and ensure data quality throughout the pipeline.

I have curated the best interview resources to crack Data Science Interviews
👇👇
https://whatsapp.com/channel/0029Va8v3eo1NCrQfGMseL2D

Like if you need similar content 😄👍

In a data science project, using multiple scalers can be beneficial when dealing with features that have different scales or distributions. Scaling is important in machine learning to ensure that all features contribute equally to the model training process and to prevent certain features from dominating others.

Here are some scenarios where using multiple scalers can be helpful in a data science project:

1. Standardization vs. Normalization: Standardization (scaling features to have a mean of 0 and a standard deviation of 1) and normalization (scaling features to a range between 0 and 1) are two common scaling techniques. Depending on the distribution of your data, you may choose to apply different scalers to different features.

2. RobustScaler vs. MinMaxScaler: RobustScaler is a good choice when dealing with outliers, as it scales the data based on percentiles rather than the mean and standard deviation. MinMaxScaler, on the other hand, scales the data to a specific range. Using both scalers can be beneficial when dealing with mixed types of data.

3. Feature engineering: In feature engineering, you may create new features that have different scales than the original features. In such cases, applying different scalers to different sets of features can help maintain consistency in the scaling process.

4. Pipeline flexibility: By using multiple scalers within a preprocessing pipeline, you can experiment with different scaling techniques and easily switch between them to see which one works best for your data.

5. Domain-specific considerations: Certain domains may require specific scaling techniques based on the nature of the data. For example, in image processing tasks, pixel values are often scaled differently than numerical features.

When using multiple scalers in a data science project, it's important to evaluate the impact of scaling on the model performance through cross-validation or other evaluation methods. Try experimenting with different scaling techniques to you find the optimal approach for your specific dataset and machine learning model.

If you want to get a job as a machine learning engineer, don’t start by diving into the hottest libraries like PyTorch,TensorFlow, Langchain, etc.

Yes, you might hear a lot about them or some other trending technology of the year...but guess what!

Technologies evolve rapidly, especially in the age of AI, but core concepts are always seen as more valuable than expertise in any particular tool. Stop trying to perform a brain surgery without knowing anything about human anatomy.

Instead, here are basic skills that will get you further than mastering any framework:


𝐌𝐚𝐭𝐡𝐞𝐦𝐚𝐭𝐢𝐜𝐬 𝐚𝐧𝐝 𝐒𝐭𝐚𝐭𝐢𝐬𝐭𝐢𝐜𝐬 - My first exposure to probability and statistics was in college, and it felt abstract at the time, but these concepts are the backbone of ML.

You can start here: Khan Academy Statistics and Probability - https://www.khanacademy.org/math/statistics-probability

𝐋𝐢𝐧𝐞𝐚𝐫 𝐀𝐥𝐠𝐞𝐛𝐫𝐚 𝐚𝐧𝐝 𝐂𝐚𝐥𝐜𝐮𝐥𝐮𝐬 - Concepts like matrices, vectors, eigenvalues, and derivatives are fundamental to understanding how ml algorithms work. These are used in everything from simple regression to deep learning.

𝐏𝐫𝐨𝐠𝐫𝐚𝐦𝐦𝐢𝐧𝐠 - Should you learn Python, Rust, R, Julia, JavaScript, etc.? The best advice is to pick the language that is most frequently used for the type of work you want to do. I started with Python due to its simplicity and extensive library support, and it remains my go-to language for machine learning tasks.

You can start here: Automate the Boring Stuff with Python - https://automatetheboringstuff.com/

𝐀𝐥𝐠𝐨𝐫𝐢𝐭𝐡𝐦 𝐔𝐧𝐝𝐞𝐫𝐬𝐭𝐚𝐧𝐝𝐢𝐧𝐠 - Understand the fundamental algorithms before jumping to deep learning. This includes linear regression, decision trees, SVMs, and clustering algorithms.

𝐃𝐞𝐩𝐥𝐨𝐲𝐦𝐞𝐧𝐭 𝐚𝐧𝐝 𝐏𝐫𝐨𝐝𝐮𝐜𝐭𝐢𝐨𝐧:
Knowing how to take a model from development to production is invaluable. This includes understanding APIs, model optimization, and monitoring. Tools like Docker and Flask are often used in this process.

𝐂𝐥𝐨𝐮𝐝 𝐂𝐨𝐦𝐩𝐮𝐭𝐢𝐧𝐠 𝐚𝐧𝐝 𝐁𝐢𝐠 𝐃𝐚𝐭𝐚:
Familiarity with cloud platforms (AWS, Google Cloud, Azure) and big data tools (Spark) is increasingly important as datasets grow larger. These skills help you manage and process large-scale data efficiently.

You can start here: Google Cloud Machine Learning - https://cloud.google.com/learn/training/machinelearning-ai

I love frameworks and libraries, and they can make anyone's job easier.

But the more solid your foundation, the easier it will be to pick up any new technologies and actually validate whether they solve your problems.

Best Data Science & Machine Learning Resources: https://topmate.io/coding/914624

All the best 👍👍

SQL can be simple—if you learn it the smart way..



If you’re aiming to become a data analyst, mastering SQL is non-negotiable.
Here’s a smart roadmap to ace it:

1. Basics First: Understand data types, simple queries (SELECT, FROM, WHERE). Master basic filtering.

2. Joins & Relationships: Dive into INNER, LEFT, RIGHT joins. Practice combining tables to extract meaningful insights.

3. Aggregations & Functions: Get comfortable with COUNT, SUM, AVG, MAX, GROUP BY, and HAVING clauses. These are essential for summarizing data.

4. Subqueries & Nested Queries: Learn how to query within queries. This is powerful for handling complex datasets.

5. Window Functions: Explore ranking, cumulative sums, and sliding windows to work with running totals and moving averages.

6. Optimization: Study indexing and query optimization for faster, more efficient queries.

7. Real-World Scenarios: Apply your SQL knowledge to solve real-world business problems.

The journey may seem tough, but each step sharpens your skills and brings you closer to data analysis excellence. Stay consistent, practice regularly, and let SQL become your superpower! 💪

Here you can find essential SQL Interview Resources👇
https://whatsapp.com/channel/0029VanC5rODzgT6TiTGoa1v

Like this post if you need more 👍❤️

Hope it helps :)

Most Asked SQL Interview Questions at MAANG Companies🔥🔥

Preparing for an SQL Interview at MAANG Companies? Here are some crucial SQL Questions you should be ready to tackle:

1. How do you retrieve all columns from a table?

SELECT * FROM table_name;

2. What SQL statement is used to filter records?

SELECT * FROM table_name
WHERE condition;

The WHERE clause is used to filter records based on a specified condition.

3. How can you join multiple tables? Describe different types of JOINs.

SELECT columns
FROM table1
JOIN table2 ON table1.column = table2.column
JOIN table3 ON table2.column = table3.column;

Types of JOINs:

1. INNER JOIN: Returns records with matching values in both tables

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

2. LEFT JOIN: Returns all records from the left table & matched records from the right table. Unmatched records will have NULL values.

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

3. RIGHT JOIN: Returns all records from the right table & matched records from the left table. Unmatched records will have NULL values.

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

4. FULL JOIN: Returns records when there is a match in either left or right table. Unmatched records will have NULL values.

SELECT * FROM table1
FULL JOIN table2 ON table1.column = table2.column;

4. What is the difference between WHERE & HAVING clauses?

WHERE: Filters records before any groupings are made.

SELECT * FROM table_name
WHERE condition;

HAVING: Filters records after groupings are made.

SELECT column, COUNT(*)
FROM table_name
GROUP BY column
HAVING COUNT(*) > value;

5. How do you calculate average, sum, minimum & maximum values in a column?

Average: SELECT AVG(column_name) FROM table_name;

Sum: SELECT SUM(column_name) FROM table_name;

Minimum: SELECT MIN(column_name) FROM table_name;

Maximum: SELECT MAX(column_name) FROM table_name;

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📊 Aggregate Functions (COUNT, SUM, AVG, MIN, MAX)

Aggregate functions are used to perform calculations on multiple rows of a table and return a single value. They're mostly used with GROUP BY, but also work standalone.

1. COUNT()
Returns the number of rows.

Example:

SELECT COUNT(*) FROM employees;

Counts all employees in the table.

You can also count only non-null values in a column:

SELECT COUNT(email) FROM customers;


2. SUM()
Adds up all the values in a numeric column.

Example:

SELECT SUM(salary) FROM employees;

Gives you the total salary payout.


3. AVG()
Calculates the average value of a numeric column.

Example:

SELECT AVG(price) FROM products;

Finds the average product price.


4. MIN()
Returns the lowest value.

Example:

SELECT MIN(salary) FROM employees;

Finds the smallest salary.


5. MAX()
Returns the highest value.

Example:

SELECT MAX(salary) FROM employees;

Finds the highest salary in the table.


Bonus Example:

SELECT
COUNT(*) AS total_orders,
SUM(amount) AS total_revenue,
AVG(amount) AS avg_order_value
FROM orders;

This gives you a quick business summary: number of orders, total revenue, and average order value.


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Data Science Learning Plan

Step 1: Mathematics for Data Science (Statistics, Probability, Linear Algebra)

Step 2: Python for Data Science (Basics and Libraries)

Step 3: Data Manipulation and Analysis (Pandas, NumPy)

Step 4: Data Visualization (Matplotlib, Seaborn, Plotly)

Step 5: Databases and SQL for Data Retrieval

Step 6: Introduction to Machine Learning (Supervised and Unsupervised Learning)

Step 7: Data Cleaning and Preprocessing

Step 8: Feature Engineering and Selection

Step 9: Model Evaluation and Tuning

Step 10: Deep Learning (Neural Networks, TensorFlow, Keras)

Step 11: Working with Big Data (Hadoop, Spark)

Step 12: Building Data Science Projects and Portfolio

Data Science Interview Resources
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If I need to teach someone data analytics from the basics, here is my strategy:

1. I will first remove the fear of tools from that person

2. i will start with the excel because it looks familiar and easy to use

3. I put more emphasis on projects like at least 5 to 6 with the excel. because in industry you learn by doing things

4. I will release the person from the tutorial hell and move into a more action oriented person

5. Then I move to the sql because every job wants it , even with the ai tools you need strong understanding for it if you are going to use it daily

6. After strong understanding, I will push the person to solve 100 to 150 Sql problems from basic to advance

7. It helps the person to develop the analytical thinking

8. Then I push the person to solve 3 case studies as it helps how we pull the data in the real life

9. Then I move the person to power bi to do again 5 projects by using either sql or excel files

10. Now the fear is removed.

11. Now I push the person to solve unguided challenges and present them by video recording as it increases the problem solving, communication and data story telling skills

12. Further it helps you to clear case study round given by most of the companies

13. Now i help the person how to present them in resume and also how these tools are used in real world.

14. You know the interesting fact, all of above is present free in youtube and I also mentor the people through existing youtube videos.

15. But people stuck in the tutorial hell, loose motivation , stay confused that they are either in the right direction or not.

16. As a personal mentor , I help them to get of the tutorial hell, set them in the right direction and they stay motivated when they start to see the difference before amd after mentorship

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Data Science is very vast field.

I saw one linkedin profile today with below skills 👇

Technical Skills:
Data Manipulation: Numpy, Pandas, BeautifulSoup, PySpark
Data Visualization: EDA- Matplotlib, Seaborn, Plotly, Tableau, PowerBI
Machine Learning: Scikit-Learn, TimeSeries Analysis
MLOPs: Gensinms, Github Actions, Gitlab CI/CD, mlflows, WandB, comet
Deep Learning: PyTorch, TensorFlow, Keras
Natural Language Processing: NLTK, NER, Spacy, word2vec, Kmeans, KNN, DBscan
Computer Vision: openCV, Yolo-V5, unet, cnn, resnet
Version Control: Git, Github, Gitlab
Database: SQL, NOSQL, Databricks
Web Frameworks: Streamlit, Flask, FastAPI, Streamlit
Generative AI - HuggingFace, LLM, Langchain, GPT-3.5, and GPT-4
Project Management and collaboration tool- JIRA, Confluence
Deployment- AWS, GCP, Docker, Google Vertex AI, Data Robot AI, Big ML, Microsoft Azure

How many of them do you have?