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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🚀 Essential Python/ Pandas snippets to explore data:
 
1.   .head() - Review top rows
2.   .tail() - Review bottom rows
3.   .info() - Summary of DataFrame
4.   .shape - Shape of DataFrame
5.   .describe() - Descriptive stats
6.   .isnull().sum() - Check missing values
7.   .dtypes - Data types of columns
8.   .unique() - Unique values in a column
9.   .nunique() - Count unique values
10.   .value_counts() - Value counts in a column
11.   .corr() - Correlation matrix

Data Structures and
Algorithms in Python

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🔟 Project Ideas for a data analyst

Customer Segmentation: Analyze customer data to segment them based on their behaviors, preferences, or demographics, helping businesses tailor their marketing strategies.

Churn Prediction: Build a model to predict customer churn, identifying factors that contribute to churn and proposing strategies to retain customers.

Sales Forecasting: Use historical sales data to create a predictive model that forecasts future sales, aiding inventory management and resource planning.

Market Basket Analysis: Analyze
transaction data to identify associations between products often purchased together, assisting retailers in optimizing product placement and cross-selling.

Sentiment Analysis: Analyze social media or customer reviews to gauge public sentiment about a product or service, providing valuable insights for brand reputation management.

Healthcare Analytics: Examine medical records to identify trends, patterns, or correlations in patient data, aiding in disease prediction, treatment optimization, and resource allocation.

Financial Fraud Detection: Develop algorithms to detect anomalous transactions and patterns in financial data, helping prevent fraud and secure transactions.

A/B Testing Analysis: Evaluate the results of A/B tests to determine the effectiveness of different strategies or changes on websites, apps, or marketing campaigns.

Energy Consumption Analysis: Analyze energy usage data to identify patterns and inefficiencies, suggesting strategies for optimizing energy consumption in buildings or industries.

Real Estate Market Analysis: Study housing market data to identify trends in property prices, rental rates, and demand, assisting buyers, sellers, and investors in making informed decisions.

Remember to choose a project that aligns with your interests and the domain you're passionate about.

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Data Analytics Projects List✨! 💼📊

Beginner-Level Projects 🏁
(Focus: Excel, SQL, data cleaning)

1️⃣ Sales performance dashboard in Excel
2️⃣ Customer feedback summary using text data
3️⃣ Clean and analyze a CSV file with missing data
4️⃣ Product inventory analysis with pivot tables
5️⃣ Use SQL to query and visualize a retail dataset
6️⃣ Create a revenue tracker by month and category
7️⃣ Analyze demographic data from a survey
8️⃣ Market share analysis across product lines
9️⃣ Simple cohort analysis using Excel
🔟 User signup trends using SQL GROUP BY and DATE

Intermediate-Level Projects 🚀
(Focus: Python, data visualization, EDA)

1️⃣ Churn analysis from telco dataset using Python
2️⃣ Power BI sales dashboard with filters & slicers
3️⃣ E-commerce data segmentation with clustering
4️⃣ Forecast site traffic using moving averages
5️⃣ Analyze Netflix/Bollywood IMDB datasets
6️⃣ A/B test results evaluation for marketing campaign
7️⃣ Customer lifetime value prediction
8️⃣ Explore correlations in vaccination or health datasets
9️⃣ Predict loan approval using logistic regression
🔟 Create a Tableau dashboard highlighting HR insights

Advanced-Level Projects 🔥
(Focus: Machine learning, big data, real-world scenarios)

1️⃣ Fraud detection using anomaly detection on banking data
2️⃣ Real-time dashboard using streaming data (Power BI + API)
3️⃣ Predictive model for sales forecasting with ML
4️⃣ NLP sentiment analysis of product reviews or tweets
5️⃣ Recommender system for e-commerce products
6️⃣ Build ETL pipeline (Python + SQL + cloud storage)
7️⃣ Analyze and visualize stock market trends
8️⃣ Big data analysis using Spark on a large dataset
9️⃣ Create a data compliance audit dashboard
🔟 Geospatial heatmap of business locations vs revenue

📂 Pro Tip: Host these on GitHub, add visuals, and explain your process—great for impressing recruiters! 🙌

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🚀 Essential Python/ Pandas snippets to explore data:
 
1.   .head() - Review top rows
2.   .tail() - Review bottom rows
3.   .info() - Summary of DataFrame
4.   .shape - Shape of DataFrame
5.   .describe() - Descriptive stats
6.   .isnull().sum() - Check missing values
7.   .dtypes - Data types of columns
8.   .unique() - Unique values in a column
9.   .nunique() - Count unique values
10.   .value_counts() - Value counts in a column
11.   .corr() - Correlation matrix

🔥 Guys, Another Big Announcement!

I’m launching a Python Interview Series 🐍💼 — your complete guide to cracking Python interviews from beginner to advanced level!

This will be a week-by-week series designed to make you interview-ready — covering core concepts, coding questions, and real interview scenarios asked by top companies.

Here’s what’s coming your way 👇

🔹 Week 1: Python Fundamentals (Beginner Level)
• Data types, variables & operators
• If-else, loops & functions
• Input/output & basic problem-solving
💡 *Practice:* Reverse string, Prime check, Factorial, Palindrome

🔹 Week 2: Data Structures in Python
• Lists, Tuples, Sets, Dictionaries
• Comprehensions (list, dict, set)
• Sorting, searching, and nested structures
💡 *Practice:* Frequency count, remove duplicates, find max/min

🔹 Week 3: Functions, Modules & File Handling
• *args, *kwargs, lambda, map/filter/reduce
• File read/write, CSV handling
• Modules & imports
💡 *Practice:* Create custom functions, read data files, handle errors

🔹 Week 4: Object-Oriented Programming (OOP)
• Classes, objects, inheritance, polymorphism
• Encapsulation & abstraction
• Magic methods (__init__, __str__)
💡 *Practice:* Build a simple class like BankAccount or StudentSystem

🔹 Week 5: Exception Handling & Logging
• try-except-else-finally
• Custom exceptions
• Logging errors & debugging best practices
💡 *Practice:* File operations with proper error handling

🔹 Week 6: Advanced Python Concepts
• Decorators, generators, iterators
• Closures & context managers
• Shallow vs deep copy
💡 *Practice:* Create your own decorator, generator examples

🔹 Week 7: Pandas & NumPy for Data Analysis
• DataFrame basics, filtering & grouping
• Handling missing data
• NumPy arrays, slicing, and aggregation
💡 *Practice:* Analyze small CSV datasets

🔹 Week 8: Python for Analytics & Visualization
• Matplotlib, Seaborn basics
• Data summarization & correlation
• Building simple dashboards
💡 *Practice:* Visualize sales or user data

🔹 Week 9: Real Interview Questions (Intermediate–Advanced)
• 50+ Python interview questions with answers
• Common logical & coding tasks
• Real company-style questions (Infosys, TCS, Deloitte, etc.)
💡 *Practice:* Solve daily problem sets

🔹 Week 10: Final Interview Prep (Mock & Revision)
• End-to-end mock interviews
• Python project discussion tips
• Resume & GitHub portfolio guidance

📌 Each week includes:
✅ Key Concepts & Examples
✅ Coding Snippets & Practice Tasks
✅ Real Interview Q&A
✅ Mini Quiz & Discussion

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Python CheatSheet 📚 ✅

1. Basic Syntax
- Print Statement: print("Hello, World!")
- Comments: # This is a comment

2. Data Types
- Integer: x = 10
- Float: y = 10.5
- String: name = "Alice"
- List: fruits = ["apple", "banana", "cherry"]
- Tuple: coordinates = (10, 20)
- Dictionary: person = {"name": "Alice", "age": 25}

3. Control Structures
- If Statement:

     if x > 10:
         print("x is greater than 10")
     

- For Loop:

     for fruit in fruits:
         print(fruit)
     

- While Loop:

     while x < 5:
         x += 1
     

4. Functions
- Define Function:

     def greet(name):
         return f"Hello, {name}!"
     

- Lambda Function: add = lambda a, b: a + b

5. Exception Handling
- Try-Except Block:

     try:
         result = 10 / 0
     except ZeroDivisionError:
         print("Cannot divide by zero.")
     

6. File I/O
- Read File:

     with open('file.txt', 'r') as file:
         content = file.read()
     

- Write File:

     with open('file.txt', 'w') as file:
         file.write("Hello, World!")
     

7. List Comprehensions
- Basic Example: squared = [x**2 for x in range(10)]
- Conditional Comprehension: even_squares = [x**2 for x in range(10) if x % 2 == 0]

8. Modules and Packages
- Import Module: import math
- Import Specific Function: from math import sqrt

9. Common Libraries
- NumPy: import numpy as np
- Pandas: import pandas as pd
- Matplotlib: import matplotlib.pyplot as plt

10. Object-Oriented Programming
- Define Class:

      class Dog:
          def __init__(self, name):
              self.name = name
          def bark(self):
              return "Woof!"
      

11. Virtual Environments
- Create Environment: python -m venv myenv
- Activate Environment:
- Windows: myenv\Scripts\activate
- macOS/Linux: source myenv/bin/activate

12. Common Commands
- Run Script: python script.py
- Install Package: pip install package_name
- List Installed Packages: pip list

This Python checklist serves as a quick reference for essential syntax, functions, and best practices to enhance your coding efficiency!

Checklist for Data Analyst: https://dataanalytics.beehiiv.com/p/data

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https://t.me/DataSimplifier

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30-day roadmap to learn Python up to an intermediate level

Week 1: Python Basics
*Day 1-2:*
- Learn about Python, its syntax, and how to install Python on your computer.
- Write your first "Hello, World!" program.
- Understand variables and data types (integers, floats, strings).

*Day 3-4:*
- Explore basic operations (arithmetic, string concatenation).
- Learn about user input and how to use the input() function.
- Practice creating and using variables.

*Day 5-7:*
- Dive into control flow with if statements, else statements, and loops (for and while).
- Work on simple programs that involve conditions and loops.

Week 2: Functions and Modules
*Day 8-9:*
- Study functions and how to define your own functions using def.
- Learn about function arguments and return values.

*Day 10-12:*
- Explore built-in functions and libraries (e.g., len(), random, math).
- Understand how to import modules and use their functions.

*Day 13-14:*
- Practice writing functions for common tasks.
- Create a small project that utilizes functions and modules.

Week 3: Data Structures
*Day 15-17:*
- Learn about lists and their operations (slicing, appending, removing).
- Understand how to work with lists of different data types.

*Day 18-19:*
- Study dictionaries and their key-value pairs.
- Practice manipulating dictionary data.

*Day 20-21:*
- Explore tuples and sets.
- Understand when and how to use each data structure.

Week 4: Intermediate Topics
*Day 22-23:*
- Study file handling and how to read/write files in Python.
- Work on projects involving file operations.

*Day 24-26:*
- Learn about exceptions and error handling.
- Explore object-oriented programming (classes and objects).

*Day 27-28:*
- Dive into more advanced topics like list comprehensions and generators.
- Study Python's built-in libraries for web development (e.g., requests).

*Day 29-30:*
- Explore additional libraries and frameworks relevant to your interests (e.g., NumPy for data analysis, Flask for web development, or Pygame for game development).
- Work on a more complex project that combines your knowledge from the past weeks.

Throughout the 30 days, practice coding daily, and don't hesitate to explore Python's documentation and online resources for additional help. You can refer this guide to help you with interview preparation.

Good luck with your Python journey 😄👍

Python is a popular programming language in the field of data analysis due to its versatility, ease of use, and extensive libraries for data manipulation, visualization, and analysis. Here are some key Python skills that are important for data analysts:

1. Basic Python Programming: Understanding basic Python syntax, data types, control structures, functions, and object-oriented programming concepts is essential for data analysis in Python.

2. NumPy: NumPy is a fundamental package for scientific computing in Python. It provides support for large multidimensional arrays and matrices, along with a collection of mathematical functions to operate on these arrays.

3. Pandas: Pandas is a powerful library for data manipulation and analysis in Python. It provides data structures like DataFrames and Series that make it easy to work with structured data and perform tasks such as filtering, grouping, joining, and reshaping data.

4. Matplotlib and Seaborn: Matplotlib is a versatile library for creating static, interactive, and animated visualizations in Python. Seaborn is built on top of Matplotlib and provides a higher-level interface for creating attractive statistical graphics.

5. Scikit-learn: Scikit-learn is a popular machine learning library in Python that provides tools for building predictive models, performing clustering and classification tasks, and evaluating model performance.

6. Jupyter Notebooks: Jupyter Notebooks are an interactive computing environment that allows you to create and share documents containing live code, equations, visualizations, and narrative text. They are commonly used by data analysts for exploratory data analysis and sharing insights.

7. SQLAlchemy: SQLAlchemy is a Python SQL toolkit and Object-Relational Mapping (ORM) library that provides a high-level interface for interacting with relational databases using Python.

8. Regular Expressions: Regular expressions (regex) are powerful tools for pattern matching and text processing in Python. They are useful for extracting specific information from text data or performing data cleaning tasks.

9. Data Visualization Libraries: In addition to Matplotlib and Seaborn, data analysts may also use other visualization libraries like Plotly, Bokeh, or Altair to create interactive visualizations in Python.

10. Web Scraping: Knowledge of web scraping techniques using libraries like BeautifulSoup or Scrapy can be useful for collecting data from websites for analysis.

By mastering these Python skills and applying them to real-world data analysis projects, you can enhance your proficiency as a data analyst and unlock new opportunities in the field.

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✅Python Checklist for Data Analysts 🧠

1. Python Basics 
   ▪ Variables, data types (int, float, str, bool) 
   ▪ Control flow: if-else, loops (for, while) 
   ▪ Functions and lambda expressions 
   ▪ List, dict, tuple, set basics

2. Data Handling & Manipulation 
   ▪ NumPy: arrays, vectorized operations, broadcasting 
   ▪ Pandas: Series & DataFrame, reading/writing CSV, Excel 
   ▪ Data inspection: head(), info(), describe() 
   ▪ Filtering, sorting, grouping (groupby), merging/joining datasets 
   ▪ Handling missing data (isnull(), fillna(), dropna())

3. Data Visualization 
   ▪ Matplotlib basics: plots, histograms, scatter plots 
   ▪ Seaborn: statistical visualizations (heatmaps, boxplots) 
   ▪ Plotly (optional): interactive charts

4. Statistics & Probability 
   ▪ Descriptive stats (mean, median, std) 
   ▪ Probability distributions, hypothesis testing (SciPy, statsmodels) 
   ▪ Correlation, covariance

5. Working with APIs & Data Sources 
   ▪ Fetching data via APIs (requests library) 
   ▪ Reading JSON, XML 
   ▪ Web scraping basics (BeautifulSoup, Scrapy)

6. Automation & Scripting 
   ▪ Automate repetitive data tasks using loops, functions 
   ▪ Excel automation (openpyxl, xlrd) 
   ▪ File handling and regular expressions

7. Machine Learning Basics (Optional starting point) 
   ▪ Scikit-learn for basic models (regression, classification) 
   ▪ Train-test split, evaluation metrics

8. Version Control & Collaboration 
   ▪ Git basics: init, commit, push, pull 
   ▪ Sharing notebooks or scripts via GitHub

9. Environment & Tools 
   ▪ Jupyter Notebook / JupyterLab for interactive analysis 
   ▪ Python IDEs (VSCode, PyCharm) 
   ▪ Virtual environments (venv, conda)

10. Projects & Portfolio 
    ▪ Analyze real datasets (Kaggle, UCI) 
    ▪ Document insights in notebooks or blogs 
    ▪ Showcase code & analysis on GitHub

💡 Tips:
⦁ Practice coding daily with mini-projects and challenges
⦁ Use interactive platforms like Kaggle, DataCamp, or LeetCode (Python)
⦁ Combine SQL + Python skills for powerful data querying & analysis

Python Programming Resources: https://whatsapp.com/channel/0029VaiM08SDuMRaGKd9Wv0L

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