🔅SQL Revision Notes for Interview💡
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7 High-Impact Portfolio Project Ideas for Aspiring Data Analysts
✅ Sales Dashboard – Use Power BI or Tableau to visualize KPIs like revenue, profit, and region-wise performance
✅ Customer Churn Analysis – Predict which customers are likely to leave using Python (Logistic Regression, EDA)
✅ Netflix Dataset Exploration – Analyze trends in content types, genres, and release years with Pandas & Matplotlib
✅ HR Analytics Dashboard – Visualize attrition, department strength, and performance reviews
✅ Survey Data Analysis – Clean, visualize, and derive insights from user feedback or product surveys
✅ E-commerce Product Analysis – Analyze top-selling products, revenue by category, and return rates
✅ Airbnb Price Predictor – Use machine learning to predict listing prices based on location, amenities, and ratings
These projects showcase real-world skills and storytelling with data.
Share with credits: https://news.1rj.ru/str/sqlspecialist
Hope it helps :)
✅ Sales Dashboard – Use Power BI or Tableau to visualize KPIs like revenue, profit, and region-wise performance
✅ Customer Churn Analysis – Predict which customers are likely to leave using Python (Logistic Regression, EDA)
✅ Netflix Dataset Exploration – Analyze trends in content types, genres, and release years with Pandas & Matplotlib
✅ HR Analytics Dashboard – Visualize attrition, department strength, and performance reviews
✅ Survey Data Analysis – Clean, visualize, and derive insights from user feedback or product surveys
✅ E-commerce Product Analysis – Analyze top-selling products, revenue by category, and return rates
✅ Airbnb Price Predictor – Use machine learning to predict listing prices based on location, amenities, and ratings
These projects showcase real-world skills and storytelling with data.
Share with credits: https://news.1rj.ru/str/sqlspecialist
Hope it helps :)
❤3
Python Cheatsheet
❤5
Beginner’s Roadmap to Learn Data Structures & Algorithms
1. Foundations: Start with the basics of programming and mathematical concepts to build a strong foundation.
2. Data Structure: Dive into essential data structures like arrays, linked lists, stacks, and queues to organise and store data efficiently.
3. Searching & Sorting: Learn various search and sort techniques to optimise data retrieval and organisation.
4. Trees & Graphs: Understand the concepts of binary trees and graph representation to tackle complex hierarchical data.
5. Recursion: Grasp the principles of recursion and how to implement recursive algorithms for problem-solving.
6. Advanced Data Structures: Explore advanced structures like hashing, heaps, and hash maps to enhance data manipulation.
7. Algorithms: Master algorithms such as greedy, divide and conquer, and dynamic programming to solve intricate problems.
8. Advanced Topics: Delve into backtracking, string algorithms, and bit manipulation for a deeper understanding.
9. Problem Solving: Practice on coding platforms like LeetCode to sharpen your skills and solve real-world algorithmic challenges.
10. Projects & Portfolio: Build real-world projects and showcase your skills on GitHub to create an impressive portfolio.
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All the best 👍👍
1. Foundations: Start with the basics of programming and mathematical concepts to build a strong foundation.
2. Data Structure: Dive into essential data structures like arrays, linked lists, stacks, and queues to organise and store data efficiently.
3. Searching & Sorting: Learn various search and sort techniques to optimise data retrieval and organisation.
4. Trees & Graphs: Understand the concepts of binary trees and graph representation to tackle complex hierarchical data.
5. Recursion: Grasp the principles of recursion and how to implement recursive algorithms for problem-solving.
6. Advanced Data Structures: Explore advanced structures like hashing, heaps, and hash maps to enhance data manipulation.
7. Algorithms: Master algorithms such as greedy, divide and conquer, and dynamic programming to solve intricate problems.
8. Advanced Topics: Delve into backtracking, string algorithms, and bit manipulation for a deeper understanding.
9. Problem Solving: Practice on coding platforms like LeetCode to sharpen your skills and solve real-world algorithmic challenges.
10. Projects & Portfolio: Build real-world projects and showcase your skills on GitHub to create an impressive portfolio.
Best DSA RESOURCES: https://topmate.io/coding/886874
All the best 👍👍
❤3
𝗣-𝗩𝗮𝗹𝘂𝗲𝘀 𝗳𝗼𝗿 𝗥𝗲𝗴𝗿𝗲𝘀𝘀𝗶𝗼𝗻 𝗠𝗼𝗱𝗲𝗹 𝗘𝘅𝗽𝗹𝗮𝗶𝗻𝗲𝗱
𝗪𝗵𝗲𝗻 𝗯𝘂𝗶𝗹𝗱𝗶𝗻𝗴 𝗮 𝗿𝗲𝗴𝗿𝗲𝘀𝘀𝗶𝗼𝗻 𝗺𝗼𝗱𝗲𝗹, 𝗻𝗼𝘁 𝗲𝘃𝗲𝗿𝘆 𝘃𝗮𝗿𝗶𝗮𝗯𝗹𝗲 𝗶𝘀 𝗰𝗿𝗲𝗮𝘁𝗲𝗱 𝗲𝗾𝘂𝗮𝗹.
Some variables will genuinely impact your predictions, while others are just background noise.
𝗧𝗵𝗲 𝗽-𝘃𝗮𝗹𝘂𝗲 𝗵𝗲𝗹𝗽𝘀 𝘆𝗼𝘂 𝗳𝗶𝗴𝘂𝗿𝗲 𝗼𝘂𝘁 𝘄𝗵𝗶𝗰𝗵 𝗶𝘀 𝘄𝗵𝗶𝗰𝗵.
𝗪𝗵𝗮𝘁 𝗲𝘅𝗮𝗰𝘁𝗹𝘆 𝗶𝘀 𝗮 𝗣-𝗩𝗮𝗹𝘂𝗲?
𝗔 𝗽-𝘃𝗮𝗹𝘂𝗲 𝗮𝗻𝘀𝘄𝗲𝗿𝘀 𝗼𝗻𝗲 𝗾𝘂𝗲𝘀𝘁𝗶𝗼𝗻:
➔ If this variable had no real effect, what’s the probability that we’d still observe results this extreme just by chance?
• 𝗟𝗼𝘄 𝗣-𝗩𝗮𝗹𝘂𝗲 (𝘂𝘀𝘂𝗮𝗹𝗹𝘆 < 0.05): Strong evidence that the variable is important.
• 𝗛𝗶𝗴𝗵 𝗣-𝗩𝗮𝗹𝘂𝗲 (> 0.05): The variable’s relationship with the output could easily be random.
𝗛𝗼𝘄 𝗣-𝗩𝗮𝗹𝘂𝗲𝘀 𝗚𝘂𝗶𝗱𝗲 𝗬𝗼𝘂𝗿 𝗥𝗲𝗴𝗿𝗲𝘀𝘀𝗶𝗼𝗻 𝗠𝗼𝗱𝗲𝗹
𝗜𝗺𝗮𝗴𝗶𝗻𝗲 𝘆𝗼𝘂’𝗿𝗲 𝗮 𝘀𝗰𝘂𝗹𝗽𝘁𝗼𝗿.
You start with a messy block of stone (all your features).
P-values are your chisel.
𝗥𝗲𝗺𝗼𝘃𝗲 the features with high p-values (not useful).
𝗞𝗲𝗲𝗽 the features with low p-values (important).
This results in a leaner, smarter model that doesn’t just memorize noise but learns real patterns.
𝗪𝗵𝘆 𝗣-𝗩𝗮𝗹𝘂𝗲𝘀 𝗠𝗮𝘁𝘁𝗲𝗿
𝗪𝗶𝘁𝗵𝗼𝘂𝘁 𝗽-𝘃𝗮𝗹𝘂𝗲𝘀, 𝗺𝗼𝗱𝗲𝗹 𝗯𝘂𝗶𝗹𝗱𝗶𝗻𝗴 𝗯𝗲𝗰𝗼𝗺𝗲𝘀 𝗴𝘂𝗲𝘀𝘀𝘄𝗼𝗿𝗸.
✅ 𝗟𝗼𝘄 𝗣-𝗩𝗮𝗹𝘂𝗲 ➔ Likely genuine effect.
❌ 𝗛𝗶𝗴𝗵 𝗣-𝗩𝗮𝗹𝘂𝗲 ➔ Likely coincidence.
𝗜𝗳 𝘆𝗼𝘂 𝗶𝗴𝗻𝗼𝗿𝗲 𝗶𝘁, 𝘆𝗼𝘂 𝗿𝗶𝘀𝗸:
• Overfitting your model with junk features
• Lowering your model’s accuracy and interpretability
• Making wrong business decisions based on faulty insights
𝗧𝗵𝗲 𝟬.𝟬𝟱 𝗧𝗵𝗿𝗲𝘀𝗵𝗼𝗹𝗱: 𝗡𝗼𝘁 𝗔 𝗠𝗮𝗴𝗶𝗰 𝗡𝘂𝗺𝗯𝗲𝗿
You’ll often hear: If p < 0.05, it’s significant!
𝗕𝘂𝘁 𝗯𝗲 𝗰𝗮𝗿𝗲𝗳𝘂𝗹.
This threshold is not universal.
• In critical fields (like medicine), you might need a much lower p-value (e.g., 0.01).
• In exploratory analysis, you might tolerate higher p-values.
Context always matters.
𝗥𝗲𝗮𝗹-𝗪𝗼𝗿𝗹𝗱 𝗔𝗱𝘃𝗶𝗰𝗲
When evaluating your regression model:
➔ 𝗗𝗼𝗻’𝘁 𝗷𝘂𝘀𝘁 𝗹𝗼𝗼𝗸 𝗮𝘁 𝗽-𝘃𝗮𝗹𝘂𝗲𝘀 𝗮𝗹𝗼𝗻𝗲.
𝗖𝗼𝗻𝘀𝗶𝗱𝗲𝗿:
• The feature’s practical importance (not just statistical)
• Multicollinearity (highly correlated variables can distort p-values)
• Overall model fit (R², Adjusted R²)
𝗜𝗻 𝗦𝗵𝗼𝗿𝘁:
𝗟𝗼𝘄 𝗣-𝗩𝗮𝗹𝘂𝗲 = 𝗧𝗵𝗲 𝗳𝗲𝗮𝘁𝘂𝗿𝗲 𝗺𝗮𝘁𝘁𝗲𝗿𝘀.
𝗛𝗶𝗴𝗵 𝗣-𝗩𝗮𝗹𝘂𝗲 = 𝗜𝘁’𝘀 𝗽𝗿𝗼𝗯𝗮𝗯𝗹𝘆 𝗷𝘂𝘀𝘁 𝗻𝗼𝗶𝘀𝗲.
𝗪𝗵𝗲𝗻 𝗯𝘂𝗶𝗹𝗱𝗶𝗻𝗴 𝗮 𝗿𝗲𝗴𝗿𝗲𝘀𝘀𝗶𝗼𝗻 𝗺𝗼𝗱𝗲𝗹, 𝗻𝗼𝘁 𝗲𝘃𝗲𝗿𝘆 𝘃𝗮𝗿𝗶𝗮𝗯𝗹𝗲 𝗶𝘀 𝗰𝗿𝗲𝗮𝘁𝗲𝗱 𝗲𝗾𝘂𝗮𝗹.
Some variables will genuinely impact your predictions, while others are just background noise.
𝗧𝗵𝗲 𝗽-𝘃𝗮𝗹𝘂𝗲 𝗵𝗲𝗹𝗽𝘀 𝘆𝗼𝘂 𝗳𝗶𝗴𝘂𝗿𝗲 𝗼𝘂𝘁 𝘄𝗵𝗶𝗰𝗵 𝗶𝘀 𝘄𝗵𝗶𝗰𝗵.
𝗪𝗵𝗮𝘁 𝗲𝘅𝗮𝗰𝘁𝗹𝘆 𝗶𝘀 𝗮 𝗣-𝗩𝗮𝗹𝘂𝗲?
𝗔 𝗽-𝘃𝗮𝗹𝘂𝗲 𝗮𝗻𝘀𝘄𝗲𝗿𝘀 𝗼𝗻𝗲 𝗾𝘂𝗲𝘀𝘁𝗶𝗼𝗻:
➔ If this variable had no real effect, what’s the probability that we’d still observe results this extreme just by chance?
• 𝗟𝗼𝘄 𝗣-𝗩𝗮𝗹𝘂𝗲 (𝘂𝘀𝘂𝗮𝗹𝗹𝘆 < 0.05): Strong evidence that the variable is important.
• 𝗛𝗶𝗴𝗵 𝗣-𝗩𝗮𝗹𝘂𝗲 (> 0.05): The variable’s relationship with the output could easily be random.
𝗛𝗼𝘄 𝗣-𝗩𝗮𝗹𝘂𝗲𝘀 𝗚𝘂𝗶𝗱𝗲 𝗬𝗼𝘂𝗿 𝗥𝗲𝗴𝗿𝗲𝘀𝘀𝗶𝗼𝗻 𝗠𝗼𝗱𝗲𝗹
𝗜𝗺𝗮𝗴𝗶𝗻𝗲 𝘆𝗼𝘂’𝗿𝗲 𝗮 𝘀𝗰𝘂𝗹𝗽𝘁𝗼𝗿.
You start with a messy block of stone (all your features).
P-values are your chisel.
𝗥𝗲𝗺𝗼𝘃𝗲 the features with high p-values (not useful).
𝗞𝗲𝗲𝗽 the features with low p-values (important).
This results in a leaner, smarter model that doesn’t just memorize noise but learns real patterns.
𝗪𝗵𝘆 𝗣-𝗩𝗮𝗹𝘂𝗲𝘀 𝗠𝗮𝘁𝘁𝗲𝗿
𝗪𝗶𝘁𝗵𝗼𝘂𝘁 𝗽-𝘃𝗮𝗹𝘂𝗲𝘀, 𝗺𝗼𝗱𝗲𝗹 𝗯𝘂𝗶𝗹𝗱𝗶𝗻𝗴 𝗯𝗲𝗰𝗼𝗺𝗲𝘀 𝗴𝘂𝗲𝘀𝘀𝘄𝗼𝗿𝗸.
✅ 𝗟𝗼𝘄 𝗣-𝗩𝗮𝗹𝘂𝗲 ➔ Likely genuine effect.
❌ 𝗛𝗶𝗴𝗵 𝗣-𝗩𝗮𝗹𝘂𝗲 ➔ Likely coincidence.
𝗜𝗳 𝘆𝗼𝘂 𝗶𝗴𝗻𝗼𝗿𝗲 𝗶𝘁, 𝘆𝗼𝘂 𝗿𝗶𝘀𝗸:
• Overfitting your model with junk features
• Lowering your model’s accuracy and interpretability
• Making wrong business decisions based on faulty insights
𝗧𝗵𝗲 𝟬.𝟬𝟱 𝗧𝗵𝗿𝗲𝘀𝗵𝗼𝗹𝗱: 𝗡𝗼𝘁 𝗔 𝗠𝗮𝗴𝗶𝗰 𝗡𝘂𝗺𝗯𝗲𝗿
You’ll often hear: If p < 0.05, it’s significant!
𝗕𝘂𝘁 𝗯𝗲 𝗰𝗮𝗿𝗲𝗳𝘂𝗹.
This threshold is not universal.
• In critical fields (like medicine), you might need a much lower p-value (e.g., 0.01).
• In exploratory analysis, you might tolerate higher p-values.
Context always matters.
𝗥𝗲𝗮𝗹-𝗪𝗼𝗿𝗹𝗱 𝗔𝗱𝘃𝗶𝗰𝗲
When evaluating your regression model:
➔ 𝗗𝗼𝗻’𝘁 𝗷𝘂𝘀𝘁 𝗹𝗼𝗼𝗸 𝗮𝘁 𝗽-𝘃𝗮𝗹𝘂𝗲𝘀 𝗮𝗹𝗼𝗻𝗲.
𝗖𝗼𝗻𝘀𝗶𝗱𝗲𝗿:
• The feature’s practical importance (not just statistical)
• Multicollinearity (highly correlated variables can distort p-values)
• Overall model fit (R², Adjusted R²)
𝗜𝗻 𝗦𝗵𝗼𝗿𝘁:
𝗟𝗼𝘄 𝗣-𝗩𝗮𝗹𝘂𝗲 = 𝗧𝗵𝗲 𝗳𝗲𝗮𝘁𝘂𝗿𝗲 𝗺𝗮𝘁𝘁𝗲𝗿𝘀.
𝗛𝗶𝗴𝗵 𝗣-𝗩𝗮𝗹𝘂𝗲 = 𝗜𝘁’𝘀 𝗽𝗿𝗼𝗯𝗮𝗯𝗹𝘆 𝗷𝘂𝘀𝘁 𝗻𝗼𝗶𝘀𝗲.
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