When starting off your data analytics journey you DON'T need to be a SQL guru from the get-go.

In fact, most SQL skills you will only learn on the job with:

- real business problems.
- actual data sets.
- imperfect data architecture.
- other people to collaborate with.

So be kind to yourself, give yourself time to grow and above all...

try to become proficient at SQL rather than perfect.

The rest will take care of itself along the way! 😉

SQL Cheatsheet 📝

This SQL cheatsheet is designed to be your quick reference guide for SQL programming. Whether you’re a beginner learning how to query databases or an experienced developer looking for a handy resource, this cheatsheet covers essential SQL topics.

1. Database Basics
- CREATE DATABASE db_name;
- USE db_name;

2. Tables
- Create Table: CREATE TABLE table_name (col1 datatype, col2 datatype);
- Drop Table: DROP TABLE table_name;
- Alter Table: ALTER TABLE table_name ADD column_name datatype;

3. Insert Data
- INSERT INTO table_name (col1, col2) VALUES (val1, val2);

4. Select Queries
- Basic Select: SELECT * FROM table_name;
- Select Specific Columns: SELECT col1, col2 FROM table_name;
- Select with Condition: SELECT * FROM table_name WHERE condition;

5. Update Data
- UPDATE table_name SET col1 = value1 WHERE condition;

6. Delete Data
- DELETE FROM table_name WHERE condition;

7. Joins
- Inner Join: SELECT * FROM table1 INNER JOIN table2 ON table1.col = table2.col;
- Left Join: SELECT * FROM table1 LEFT JOIN table2 ON table1.col = table2.col;
- Right Join: SELECT * FROM table1 RIGHT JOIN table2 ON table1.col = table2.col;

8. Aggregations
- Count: SELECT COUNT(*) FROM table_name;
- Sum: SELECT SUM(col) FROM table_name;
- Group By: SELECT col, COUNT(*) FROM table_name GROUP BY col;

9. Sorting & Limiting
- Order By: SELECT * FROM table_name ORDER BY col ASC|DESC;
- Limit Results: SELECT * FROM table_name LIMIT n;

10. Indexes
- Create Index: CREATE INDEX idx_name ON table_name (col);
- Drop Index: DROP INDEX idx_name;

11. Subqueries
- SELECT * FROM table_name WHERE col IN (SELECT col FROM other_table);

12. Views
- Create View: CREATE VIEW view_name AS SELECT * FROM table_name;
- Drop View: DROP VIEW view_name;

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🚀 Complete Roadmap to Become a Data Scientist in 5 Months

📅 Week 1-2: Fundamentals
✅ Day 1-3: Introduction to Data Science, its applications, and roles.
✅ Day 4-7: Brush up on Python programming 🐍.
✅ Day 8-10: Learn basic statistics 📊 and probability 🎲.

🔍 Week 3-4: Data Manipulation & Visualization
📝 Day 11-15: Master Pandas for data manipulation.
📈 Day 16-20: Learn Matplotlib & Seaborn for data visualization.

🤖 Week 5-6: Machine Learning Foundations
🔬 Day 21-25: Introduction to scikit-learn.
📊 Day 26-30: Learn Linear & Logistic Regression.

🏗 Week 7-8: Advanced Machine Learning
🌳 Day 31-35: Explore Decision Trees & Random Forests.
📌 Day 36-40: Learn Clustering (K-Means, DBSCAN) & Dimensionality Reduction.

🧠 Week 9-10: Deep Learning
🤖 Day 41-45: Basics of Neural Networks with TensorFlow/Keras.
📸 Day 46-50: Learn CNNs & RNNs for image & text data.

🏛 Week 11-12: Data Engineering
🗄 Day 51-55: Learn SQL & Databases.
🧹 Day 56-60: Data Preprocessing & Cleaning.

📊 Week 13-14: Model Evaluation & Optimization
📏 Day 61-65: Learn Cross-validation & Hyperparameter Tuning.
📉 Day 66-70: Understand Evaluation Metrics (Accuracy, Precision, Recall, F1-score).

🏗 Week 15-16: Big Data & Tools
🐘 Day 71-75: Introduction to Big Data Technologies (Hadoop, Spark).
☁️ Day 76-80: Learn Cloud Computing (AWS, GCP, Azure).

🚀 Week 17-18: Deployment & Production
🛠 Day 81-85: Deploy models using Flask or FastAPI.
📦 Day 86-90: Learn Docker & Cloud Deployment (AWS, Heroku).

🎯 Week 19-20: Specialization
📝 Day 91-95: Choose NLP or Computer Vision, based on your interest.

🏆 Week 21-22: Projects & Portfolio
📂 Day 96-100: Work on Personal Data Science Projects.

💬 Week 23-24: Soft Skills & Networking
🎤 Day 101-105: Improve Communication & Presentation Skills.
🌐 Day 106-110: Attend Online Meetups & Forums.

🎯 Week 25-26: Interview Preparation
💻 Day 111-115: Practice Coding Interviews (LeetCode, HackerRank).
📂 Day 116-120: Review your projects & prepare for discussions.

👨‍💻 Week 27-28: Apply for Jobs
📩 Day 121-125: Start applying for Entry-Level Data Scientist positions.

🎤 Week 29-30: Interviews
📝 Day 126-130: Attend Interviews & Practice Whiteboard Problems.

🔄 Week 31-32: Continuous Learning
📰 Day 131-135: Stay updated with the Latest Data Science Trends.

🏆 Week 33-34: Accepting Offers
📝 Day 136-140: Evaluate job offers & Negotiate Your Salary.

🏢 Week 35-36: Settling In
🎯 Day 141-150: Start your New Data Science Job, adapt & keep learning!

🎉 Enjoy Learning & Build Your Dream Career in Data Science! 🚀🔥

🔰 Data Science Roadmap for Beginners 2025
├── 📘 What is Data Science?
├── 🧠 Data Science vs Data Analytics vs Machine Learning
├── 🛠 Tools of the Trade (Python, R, Excel, SQL)
├── 🐍 Python for Data Science (NumPy, Pandas, Matplotlib)
├── 🔢 Statistics & Probability Basics
├── 📊 Data Visualization (Matplotlib, Seaborn, Plotly)
├── 🧼 Data Cleaning & Preprocessing
├── 🧮 Exploratory Data Analysis (EDA)
├── 🧠 Introduction to Machine Learning
├── 📦 Supervised vs Unsupervised Learning
├── 🤖 Popular ML Algorithms (Linear Reg, KNN, Decision Trees)
├── 🧪 Model Evaluation (Accuracy, Precision, Recall, F1 Score)
├── 🧰 Model Tuning (Cross Validation, Grid Search)
├── ⚙️ Feature Engineering
├── 🏗 Real-world Projects (Kaggle, UCI Datasets)
├── 📈 Basic Deployment (Streamlit, Flask, Heroku)
├── 🔁 Continuous Learning: Blogs, Research Papers, Competitions

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Data Science Interview Questions

1. What are the different subsets of SQL?

Data Definition Language (DDL) – It allows you to perform various operations on the database such as CREATE, ALTER, and DELETE objects.
Data Manipulation Language(DML) – It allows you to access and manipulate data. It helps you to insert, update, delete and retrieve data from the database.
Data Control Language(DCL) – It allows you to control access to the database. Example – Grant, Revoke access permissions.

2. List the different types of relationships in SQL.

There are different types of relations in the database:
One-to-One – This is a connection between two tables in which each record in one table corresponds to the maximum of one record in the other.
One-to-Many and Many-to-One – This is the most frequent connection, in which a record in one table is linked to several records in another.
Many-to-Many – This is used when defining a relationship that requires several instances on each sides.
Self-Referencing Relationships – When a table has to declare a connection with itself, this is the method to employ.

3. How to create empty tables with the same structure as another table?

To create empty tables:
Using the INTO operator to fetch the records of one table into a new table while setting a WHERE clause to false for all entries, it is possible to create empty tables with the same structure. As a result, SQL creates a new table with a duplicate structure to accept the fetched entries, but nothing is stored into the new table since the WHERE clause is active.

4. What is Normalization and what are the advantages of it?

Normalization in SQL is the process of organizing data to avoid duplication and redundancy. Some of the advantages are:
Better Database organization
More Tables with smaller rows
Efficient data access
Greater Flexibility for Queries
Quickly find the information
Easier to implement Security

Complete Data Science Roadmap
👇👇

1. Introduction to Data Science
- Overview and Importance
- Data Science Lifecycle
- Key Roles (Data Scientist, Analyst, Engineer)

2. Mathematics and Statistics
- Probability and Distributions
- Descriptive/Inferential Statistics
- Hypothesis Testing
- Linear Algebra and Calculus Basics

3. Programming Languages
- Python: NumPy, Pandas, Matplotlib
- R: dplyr, ggplot2
- SQL: Joins, Aggregations, CRUD

4. Data Collection & Preprocessing
- Data Cleaning and Wrangling
- Handling Missing Data
- Feature Engineering

5. Exploratory Data Analysis (EDA)
- Summary Statistics
- Data Visualization (Histograms, Box Plots, Correlation)

6. Machine Learning
- Supervised (Linear/Logistic Regression, Decision Trees)
- Unsupervised (K-Means, PCA)
- Model Selection and Cross-Validation

7. Advanced Machine Learning
- SVM, Random Forests, Boosting
- Neural Networks Basics

8. Deep Learning
- Neural Networks Architecture
- CNNs for Image Data
- RNNs for Sequential Data

9. Natural Language Processing (NLP)
- Text Preprocessing
- Sentiment Analysis
- Word Embeddings (Word2Vec)

10. Data Visualization & Storytelling
- Dashboards (Tableau, Power BI)
- Telling Stories with Data

11. Model Deployment
- Deploy with Flask or Django
- Monitoring and Retraining Models

12. Big Data & Cloud
- Introduction to Hadoop, Spark
- Cloud Tools (AWS, Google Cloud)

13. Data Engineering Basics
- ETL Pipelines
- Data Warehousing (Redshift, BigQuery)

14. Ethics in Data Science
- Ethical Data Usage
- Bias in AI Models

15. Tools for Data Science
- Jupyter, Git, Docker

16. Career Path & Certifications
- Building a Data Science Portfolio

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Best Resources to learn Data Science 👇👇

Python Tutorial

Data Science Course by Kaggle

Machine Learning Course by Google

Best Data Science & Machine Learning Resources

Interview Process for Data Science Role at Amazon

Python Interview Resources

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Common Machine Learning Algorithms!

1️⃣ Linear Regression
->Used for predicting continuous values.
->Models the relationship between dependent and independent variables by fitting a linear equation.

2️⃣ Logistic Regression
->Ideal for binary classification problems.
->Estimates the probability that an instance belongs to a particular class.

3️⃣ Decision Trees
->Splits data into subsets based on the value of input features.
->Easy to visualize and interpret but can be prone to overfitting.

4️⃣ Random Forest
->An ensemble method using multiple decision trees.
->Reduces overfitting and improves accuracy by averaging multiple trees.

5️⃣ Support Vector Machines (SVM)
->Finds the hyperplane that best separates different classes.
->Effective in high-dimensional spaces and for classification tasks.

6️⃣ k-Nearest Neighbors (k-NN)
->Classifies data based on the majority class among the k-nearest neighbors.
->Simple and intuitive but can be computationally intensive.

7️⃣ K-Means Clustering
->Partitions data into k clusters based on feature similarity.
->Useful for market segmentation, image compression, and more.

8️⃣ Naive Bayes
->Based on Bayes' theorem with an assumption of independence among predictors.
->Particularly useful for text classification and spam filtering.

9️⃣ Neural Networks
->Mimic the human brain to identify patterns in data.
->Power deep learning applications, from image recognition to natural language processing.

🔟 Gradient Boosting Machines (GBM)
->Combines weak learners to create a strong predictive model.
->Used in various applications like ranking, classification, and regression.

ENJOY LEARNING 👍👍

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We’ve officially hit 2.5 Million followers — and it’s time to level up together! ❤️

I’m launching a Python Projects Series — designed for beginners to those preparing for technical interviews or building real-world projects.

This will be a step-by-step, hands-on journey — where you’ll build useful Python projects with clear code, explanations, and mini-quizzes!

Here’s what we’ll cover:

🔹 Week 1: Python Mini Projects (Daily Practice)
⦁ Calculator
⦁ To-Do List (CLI)
⦁ Number Guessing Game
⦁ Unit Converter
⦁ Digital Clock

🔹 Week 2: Data Handling & APIs
⦁ Read/Write CSV & Excel files
⦁ JSON parsing
⦁ API Calls using Requests
⦁ Weather App using OpenWeather API
⦁ Currency Converter using Real-time API

🔹 Week 3: Automation with Python
⦁ File Organizer Script
⦁ Email Sender
⦁ WhatsApp Automation
⦁ PDF Merger
⦁ Excel Report Generator

🔹 Week 4: Data Analysis with Pandas & Matplotlib
⦁ Load & Clean CSV
⦁ Data Aggregation
⦁ Data Visualization
⦁ Trend Analysis
⦁ Dashboard Basics

🔹 Week 5: AI & ML Projects (Beginner Friendly)
⦁ Predict House Prices
⦁ Email Spam Classifier
⦁ Sentiment Analysis
⦁ Image Classification (Intro)
⦁ Basic Chatbot

📌 Each project includes: 
✅ Problem Statement 
✅ Code with explanation 
✅ Sample input/output 
✅ Learning outcome 
✅ Mini quiz

💬 React ❤️ if you're ready to build some projects together!

You can access it for free here
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Data Science Interview Questions 🚀

1. What is Data Science and how does it differ from Data Analytics?
2. How do you handle missing or duplicate data?
3. Explain supervised vs unsupervised learning.
4. What is overfitting and how do you prevent it?
5. Describe the bias-variance tradeoff.
6. What is cross-validation and why is it important?
7. What are key evaluation metrics for classification models?
8. What is feature engineering? Give examples.
9. Explain principal component analysis (PCA).
10. Difference between classification and regression algorithms.
11. What is a confusion matrix?
12. Explain bagging vs boosting.
13. Describe decision trees and random forests.
14. What is gradient descent?
15. What are regularization techniques and why use them?
16. How do you handle imbalanced datasets?
17. What is hypothesis testing and p-values?
18. Explain clustering and k-means algorithm.
19. How do you handle unstructured data?
20. What is text mining and sentiment analysis?
21. How do you select important features?
22. What is ensemble learning?
23. Basics of time series analysis.
24. How do you tune hyperparameters?
25. What are activation functions in neural networks?
26. Explain transfer learning.
27. How do you deploy machine learning models?
28. What are common challenges in big data?
29. Define ROC curve and AUC score.
30. What is deep learning?
31. What is reinforcement learning?
32. What tools and libraries do you use?
33. How do you interpret model results for non-technical audiences?
34. What is dimensionality reduction?
35. Handling categorical variables in machine learning.
36. What is exploratory data analysis (EDA)?
37. Explain t-test and chi-square test.
38. How do you ensure fairness and avoid bias in models?
39. Describe a complex data problem you solved.
40. How do you stay updated with new data science trends?

React ❤️ for the detailed answers

Data Science Interview Questions With Answers Part-1 👇

1. What is Data Science and how does it differ from Data Analytics? 
   Data Science is a multidisciplinary field using algorithms, statistics, and programming to extract insights and predict future trends from structured and unstructured data. It focuses on asking the big, strategic questions and uses advanced techniques like machine learning. 
   Data Analytics, by contrast, focuses on analyzing past data to find actionable answers to specific business questions, often using simpler statistical methods and reporting tools. Simply put, Data Science looks forward, while Data Analytics looks backward (sources,,).

————————

2. How do you handle missing or duplicate data?
⦁ Missing data: techniques include removing rows/columns, imputing values with mean/median/mode, or using predictive models.
⦁ Duplicate data: identify duplicates using functions like duplicated() and remove or merge them depending on context. Handling depends on data quality needs and model goals.

————————

3. Explain supervised vs unsupervised learning.
⦁ Supervised learning uses labeled data to train models that predict outputs for new inputs (e.g., classification, regression).
⦁ Unsupervised learning finds patterns or structures in unlabeled data (e.g., clustering, dimensionality reduction).

————————

4. What is overfitting and how do you prevent it? 
   Overfitting is when a model captures noise or specific patterns in training data, resulting in poor generalization to unseen data. Prevention includes cross-validation, pruning, regularization, early stopping, and using simpler models.

————————

5. Describe the bias-variance tradeoff.
⦁ Bias measures error from incorrect assumptions (underfitting), while variance measures sensitivity to training data (overfitting).
⦁ The tradeoff is balancing model complexity so it generalizes well — neither too simple (high bias) nor too complex (high variance).

————————

6. What is cross-validation and why is it important? 
   Cross-validation divides data into subsets to train and validate models multiple times, improving performance estimation and reducing overfitting risks by ensuring the model works well on unseen data.

————————

7. What are key evaluation metrics for classification models? 
   Common metrics: Accuracy, Precision, Recall, F1-score, ROC-AUC, Confusion Matrix components (TP, FP, FN, TN), depending on dataset balance and business context.

————————

8. What is feature engineering? Give examples. 
   Feature engineering creates new input variables to improve model performance, e.g., extracting day of the week from timestamps, encoding categorical variables, normalizing numeric features, or creating interaction terms.

————————

9. Explain principal component analysis (PCA). 
   PCA reduces data dimensionality by transforming original features into uncorrelated principal components that capture the most variance, simplifying models while preserving information.

————————

10. Difference between classification and regression algorithms.
⦁ Classification predicts discrete labels or classes (e.g., spam/not spam).
⦁ Regression predicts continuous numerical values (e.g., house prices).

React ♥️ for Part-2

Data Science Interview Questions With Answers Part-2

11. What is a confusion matrix?
A confusion matrix is a table used to evaluate classification models by showing true positives (TP), false positives (FP), true negatives (TN), and false negatives (FN), helping calculate accuracy, precision, recall, and F1-score.

12. Explain bagging vs boosting.
⦁ Bagging (Bootstrap Aggregating) builds multiple independent models on random data subsets and averages results to reduce variance (e.g., Random Forest).
⦁ Boosting builds models sequentially, each correcting errors of the previous to reduce bias (e.g., AdaBoost, Gradient Boosting).

13. Describe decision trees and random forests.
⦁ Decision trees split data based on feature thresholds to make predictions in a tree-like model.
⦁ Random forests are an ensemble of decision trees built on random data and feature subsets, improving accuracy and reducing overfitting.

14. What is gradient descent?
An optimization algorithm that iteratively adjusts model parameters to minimize a loss function by moving in the direction of steepest descent (gradient).

15. What are regularization techniques and why use them?
Regularization (like L1/Lasso and L2/Ridge) adds penalty terms to loss functions to prevent overfitting by constraining model complexity and shrinking coefficients.

16. How do you handle imbalanced datasets?
Methods include resampling (oversampling minority, undersampling majority), synthetic data generation (SMOTE), using appropriate evaluation metrics, and algorithms robust to imbalance.

17. What is hypothesis testing and p-values?
Hypothesis testing assesses if a claim about data is statistically significant. The p-value indicates the probability that the observed data occurred under the null hypothesis; a low p-value (<0.05) usually leads to rejecting the null.

18. Explain clustering and k-means algorithm.
Clustering groups similar data points without labels. K-means partitions data into k clusters by iteratively assigning points to nearest centroids and recalculating centroids until convergence.

19. How do you handle unstructured data?
Techniques include text processing (tokenization, stemming), image/audio processing with specialized models (CNNs, RNNs), and converting raw data into structured features for analysis.

20. What is text mining and sentiment analysis?
Text mining extracts meaningful information from text data, while sentiment analysis classifies text by emotional tone (positive, negative, neutral), often using NLP techniques.

React ♥️ for Part-3