✅ 15 Power BI Interview Questions for Freshers 📊💻

1️⃣ What is Power BI and what is it used for?
Answer: Power BI is a business analytics tool by Microsoft to visualize data, create reports, and share insights across organizations.

2️⃣ What are the main components of Power BI?
Answer: Power BI Desktop, Power BI Service (Cloud), Power BI Mobile, Power BI Gateway, and Power BI Report Server.

3️⃣ What is a DAX in Power BI?
Answer: Data Analysis Expressions (DAX) is a formula language used to create custom calculations in Power BI.

4️⃣ What is the difference between a calculated column and a measure?
Answer: Calculated columns are row-level computations stored in the table. Measures are aggregations computed at query time.

5️⃣ What is the difference between Power BI Desktop and Power BI Service?
Answer: Desktop is for building reports and data modeling. Service is for publishing, sharing, and collaboration online.

6️⃣ What is a data model in Power BI?
Answer: A data model organizes tables, relationships, and calculations to efficiently analyze and visualize data.

7️⃣ What is the difference between DirectQuery and Import mode?
Answer: Import loads data into Power BI, faster for analysis. DirectQuery queries the source directly, no data is imported.

8️⃣ What are slicers in Power BI?
Answer: Visual filters that allow users to dynamically filter report data.

9️⃣ What is Power Query?
Answer: A data connection and transformation tool in Power BI used for cleaning and shaping data before loading.

1️⃣0️⃣ What is the difference between a table visual and a matrix visual?
Answer: Table displays data in simple rows and columns. Matrix allows grouping, row/column hierarchies, and aggregations.

1️⃣1️⃣ What is a Power BI dashboard?
Answer: A single-page collection of visualizations from multiple reports for quick insights.

1️⃣2️⃣ What is a relationship in Power BI?
Answer: Links between tables that define how data is connected for accurate aggregations and filtering.

1️⃣3️⃣ What are filters in Power BI?
Answer: Visual-level, page-level, or report-level filters to restrict data shown in reports.

1️⃣4️⃣ What is Power BI Gateway?
Answer: A bridge between on-premise data sources and Power BI Service for scheduled refreshes.

1️⃣5️⃣ What is the difference between a report and a dashboard?
Answer: Reports can have multiple pages and visuals; dashboards are single-page, with pinned visuals from reports.

Power BI Resources: https://whatsapp.com/channel/0029Vai1xKf1dAvuk6s1v22c

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✅ 15 Excel Interview Questions for Freshers 📊🧠

1️⃣ What is Microsoft Excel used for?
Answer: Excel is a spreadsheet program used for data entry, analysis, calculations, and visualization.

2️⃣ What is a cell in Excel?
Answer: A cell is the intersection of a row and column where data is entered (e.g., A1, B2).

3️⃣ What is the difference between a workbook and a worksheet?
Answer: A workbook is the entire Excel file. A worksheet is a single tab/sheet within that file.

4️⃣ What are formulas in Excel?
Answer: Formulas are expressions used to perform calculations using cell references and operators.

5️⃣ What is the difference between a formula and a function?
Answer: A formula is manually written; a function is a built-in command like SUM(), AVERAGE().

6️⃣ What does the VLOOKUP function do?
Answer: Searches for a value in the first column of a table and returns data from another column.

7️⃣ What is the difference between absolute and relative cell references?
Answer: Relative references (A1) change when copied; absolute references (A1) stay fixed.

8️⃣ What is conditional formatting?
Answer: It highlights cells based on rules (e.g., color cells above 100 in red).

9️⃣ How do you create a chart in Excel?
Answer: Select data → Insert → Choose chart type (e.g., bar, line, pie).

1️⃣0️⃣ What is a Pivot Table?
Answer: A tool to summarize, group, and analyze large data sets interactively.

1️⃣1️⃣ What is the IF function?
Answer: A logical function: IF(condition, value_if_true, value_if_false).

1️⃣2️⃣ What is the use of data validation?
Answer: Restricts data entry to specific types (e.g., numbers only, dropdown lists).

1️⃣3️⃣ How do you protect a worksheet?
Answer: Go to Review → Protect Sheet → Set password and options.

1️⃣4️⃣ What is the CONCATENATE function used for?
Answer: Combines text from multiple cells into one. (Now replaced by TEXTJOIN or CONCAT).

1️⃣5️⃣ What are Excel shortcuts you should know?
Answer:
- Ctrl + C: Copy
- Ctrl + V: Paste
- Ctrl + Z: Undo
- Ctrl + Shift + L: Toggle filter

Excel Resources: https://whatsapp.com/channel/0029VaifY548qIzv0u1AHz3i

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How to Learn Python for Data Analytics in 2025 📊✨

✅ Tip 1: Master Python Basics
Start with:
⦁ Variables, Data Types (list, dict, tuple)
⦁ Loops, Conditionals, Functions
⦁ Basic I/O and built-in functions
Dive into freeCodeCamp's Python cert for hands-on coding right away—it's interactive and builds confidence fast.

✅ Tip 2: Learn Essential Libraries
Get comfortable with:
⦁ NumPy – for arrays and numerical operations (e.g., vector math on large datasets)
⦁ pandas – for data manipulation & analysis (DataFrames are game-changers for cleaning)
⦁ matplotlib & seaborn – for data visualization
Simplilearn's 2025 full course covers these with real demos, including NumPy array tricks like summing rows/columns.

✅ Tip 3: Explore Real Datasets
Practice using open datasets from:
⦁ Kaggle (competitions for portfolio gold)
⦁ UCI Machine Learning Repository
⦁ data.gov (US) or data.gov.in for local flavor
GeeksforGeeks has tutorials loading CSVs and preprocessing—start with Titanic data for quick wins.

✅ Tip 4: Data Cleaning & Preprocessing
Learn to:
⦁ Handle missing values (pandas dropna() or fillna())
⦁ Filter, group & sort data (groupby() magic)
⦁ Merge/join multiple data sources (pd.merge())
W3Schools emphasizes this in their Data Science track—practice on messy Excel imports to mimic real jobs.

✅ Tip 5: Data Visualization Skills
Use:
⦁ matplotlib for basic charts (histograms, scatters)
⦁ seaborn for statistical plots (heatmaps for correlations)
⦁ plotly for interactive dashboards (zoomable graphs for reports)
Harvard's intro course on edX teaches plotting with real science data—pair it with Seaborn for pro-level insights.

✅ Tip 6: Work with Excel & CSV
⦁ Read/write CSVs with pandas (pd.read_csv() is your best friend)
⦁ Automate Excel reports using openpyxl or xlsxwriter (for formatted outputs)
Coursera's Google Data Analytics with Python integrates this seamlessly—export to Excel for stakeholder shares.

✅ Tip 7: Learn SQL Integration
Use pandas with SQL queries using sqlite3 or SQLAlchemy (pd.read_sql())
Combine with your SQL knowledge for hybrid queries—Intellipaat's free YouTube course shows ETL pipelines blending both.

✅ Tip 8: Explore Time Series & Grouped Data
⦁ Use resample(), groupby(), and rolling averages (for trends over time)
⦁ Learn datetime operations (pd.to_datetime())
Essential for stock or sales analysis—Simplilearn's course includes time-based EDA projects.

✅ Tip 9: Build Analytics Projects
⦁ Sales dashboard (Plotly + Streamlit for web apps)
⦁ Customer churn analysis (logistic regression basics)
⦁ Market trend visualizations
⦁ Web scraping + analytics (BeautifulSoup + Pandas)
freeCodeCamp ends with 5 portfolio projects—deploy on GitHub Pages to impress recruiters.

✅ Tip 10: Share & Document Your Work
Upload projects on GitHub
Write short case studies or LinkedIn posts
Visibility = Opportunity
Join Kaggle discussions or Reddit's r/datascience for feedback—networking lands gigs in 2025's remote market.

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✅ Top 5 SQL Aggregate Functions with Examples 📊💡

1️⃣ COUNT()
Counts rows or non-null values—use COUNT(*) for total rows, COUNT(column) to skip nulls.
Example:

SELECT COUNT(*) AS total_employees FROM Employees;

Tip: In a 1k-row table, it returns 1k; great for validating data completeness.

2️⃣ SUM()
Adds up numeric values—ignores nulls automatically.
Example:

SELECT SUM(salary) AS total_salary FROM Employees;

Tip: For March orders totaling $60, it sums to 60; pair with WHERE for filtered totals like monthly payroll.

3️⃣ AVG()
Calculates average of numeric values—also skips nulls, divides sum by non-null count.
Example:

SELECT AVG(salary) AS average_salary FROM Employees;

Tip: Two orders at $20/$40 avg to 30; use for trends, like mean salary ~$75k in tech firms.

4️⃣ MAX()
Finds the highest value in a column—works on numbers, dates, strings.
Example:

SELECT MAX(salary) AS highest_salary FROM Employees;

Tip: Max order of $40 in a set; useful for peaks, like top sales $150k.

5️⃣ MIN()
Finds the lowest value in a column—similar to MAX but for mins.
Example:

SELECT MIN(salary) AS lowest_salary FROM Employees;

Tip: Min order of $10; spot outliers, like entry-level pay ~$50k.

Bonus Combo Query:

SELECT COUNT(*) AS total,
       SUM(salary) AS total_pay,
       AVG(salary) AS avg_pay,
       MAX(salary) AS max_pay,
       MIN(salary) AS min_pay
FROM Employees;

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✅ SQL Interview Challenge – Filter Top N Records per Group 🧠💾

🧑‍💼 Interviewer: How would you fetch the top 2 highest-paid employees per department?

👨‍💻 Me: Use ROW_NUMBER() with a PARTITION BY clause—it's a window function that numbers rows uniquely within groups, resetting per partition for precise top-N filtering.

🔹 SQL Query:

SELECT *
FROM (
  SELECT name, department, salary,
         ROW_NUMBER() OVER (PARTITION BY department ORDER BY salary DESC) AS rn
  FROM employees
) AS ranked
WHERE rn <= 2;

✔ Why it works:
– PARTITION BY department resets row numbers (starting at 1) for each dept group, treating them as mini-tables.
– ORDER BY salary DESC ranks highest first within each partition.
– WHERE rn <= 2 grabs the top 2 per group—subquery avoids duplicates in complex joins!

💡 Pro Tip: Swap to RANK() if ties get equal ranks (e.g., two at #1 means next is #3, but you might get 3 rows); DENSE_RANK() avoids gaps. For big datasets, this scales well in SQL Server or Postgres.

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🧑‍💼 Interviewer: What’s the difference between DELETE and TRUNCATE?

👨‍💻 Me: Both commands are used to remove data from a table, but they work differently:

🔹 DELETE 
– Removes rows one by one, based on a WHERE condition (optional). 
– Logs each row deletion, so it’s slower. 
– Can be rolled back if used within a transaction. 
– Triggers can fire on deletion.

🔹 TRUNCATE 
– Removes all rows instantly—no WHERE clause allowed. 
– Faster, uses minimal logging. 
– Cannot delete specific rows—it's all or nothing. 
– Usually can’t be rolled back in some databases.

🧪 Example:

-- DELETE only inactive users
DELETE FROM users WHERE status = 'inactive';

-- TRUNCATE entire users table
TRUNCATE TABLE users;

💡 Tip: Use DELETE when you need conditions. Use TRUNCATE for a quick full cleanup.

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Python Beginner Roadmap 🐍

📂 Start Here
∟📂 Install Python & VS Code
∟📂 Learn How to Run Python Files

📂 Python Basics
∟📂 Variables & Data Types
∟📂 Input & Output
∟📂 Operators (Arithmetic, Comparison)
∟📂 if, else, elif
∟📂 for & while loops

📂 Data Structures
∟📂 Lists
∟📂 Tuples
∟📂 Sets
∟📂 Dictionaries

📂 Functions
∟📂 Defining & Calling Functions
∟📂 Arguments & Return Values

📂 Basic File Handling
∟📂 Read & Write to Files (.txt)

📂 Practice Projects
∟📌 Calculator
∟📌 Number Guessing Game
∟📌 To-Do List (store in file)

📂 ✅ Move to Next Level (Only After Basics)
∟📂 Learn Modules & Libraries
∟📂 Small Real-World Scripts

For detailed explanation, join this channel 👇
https://whatsapp.com/channel/0029Vau5fZECsU9HJFLacm2a

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SQL Beginner Roadmap 🗄️

📂 Start Here
∟📂 Install SQL Server / MySQL / SQLite
∟📂 Learn How to Run SQL Queries

📂 SQL Basics
∟📂 What is SQL?
∟📂 Basic SELECT Statements
∟📂 Filtering with WHERE Clause
∟📂 Sorting with ORDER BY
∟📂 Using LIMIT / TOP

📂 Data Manipulation
∟📂 INSERT INTO
∟📂 UPDATE
∟📂 DELETE

📂 Table Management
∟📂 CREATE TABLE
∟📂 ALTER TABLE
∟📂 DROP TABLE

📂 SQL Joins
∟📂 INNER JOIN
∟📂 LEFT JOIN
∟📂 RIGHT JOIN
∟📂 FULL OUTER JOIN

📂 Advanced Queries
∟📂 GROUP BY & HAVING
∟📂 Subqueries
∟📂 Aggregate Functions (COUNT, SUM, AVG)

📂 Practice Projects
∟📌 Build a Simple Library DB
∟📌 Employee Management System
∟📌 Sales Report Analysis

📂 ✅ Move to Next Level (Only After Basics)
∟📂 Learn Indexing & Performance Tuning
∟📂 Stored Procedures & Triggers
∟📂 Database Design & Normalization

Credits: https://whatsapp.com/channel/0029VanC5rODzgT6TiTGoa1v

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✅ Data Analyst Interview Questions for Freshers 📊

1) What is the role of a data analyst?
Answer: A data analyst collects, processes, and performs statistical analyses on data to provide actionable insights that support business decision-making.

2) What are the key skills required for a data analyst?
Answer: Strong skills in SQL, Excel, data visualization tools (like Tableau or Power BI), statistical analysis, and problem-solving abilities are essential.

3) What is data cleaning?
Answer: Data cleaning involves identifying and correcting inaccuracies, inconsistencies, or missing values in datasets to improve data quality.

4) What is the difference between structured and unstructured data?
Answer: Structured data is organized in rows and columns (e.g., spreadsheets), while unstructured data includes formats like text, images, and videos that lack a predefined structure.

5) What is a KPI?
Answer: KPI stands for Key Performance Indicator, which is a measurable value that demonstrates how effectively a company is achieving its business goals.

6) What tools do you use for data analysis?
Answer: Common tools include Excel, SQL, Python (with libraries like Pandas), R, Tableau, and Power BI.

7) Why is data visualization important?
Answer: Data visualization helps translate complex data into understandable charts and graphs, making it easier for stakeholders to grasp insights and trends.

8) What is a pivot table?
Answer: A pivot table is a feature in Excel that allows you to summarize, analyze, and explore data by reorganizing and grouping it dynamically.

9) What is correlation?
Answer: Correlation measures the statistical relationship between two variables, indicating whether they move together and how strongly.

10) What is a data warehouse?
Answer: A data warehouse is a centralized repository that consolidates data from multiple sources, optimized for querying and analysis.

11) Explain the difference between INNER JOIN and OUTER JOIN in SQL.
Answer: INNER JOIN returns only the matching rows between two tables, while OUTER JOIN returns all matching rows plus unmatched rows from one or both tables, depending on whether it’s LEFT, RIGHT, or FULL OUTER JOIN.

12) What is hypothesis testing?
Answer: Hypothesis testing is a statistical method used to determine if there is enough evidence in a sample to infer that a certain condition holds true for the entire population.

13) What is the difference between mean, median, and mode?
Answer:
⦁ Mean: The average of all numbers.
⦁ Median: The middle value when data is sorted.
⦁ Mode: The most frequently occurring value in a dataset.

14) What is data normalization?
Answer: Normalization is the process of organizing data to reduce redundancy and improve integrity, often by dividing data into related tables.

15) How do you handle missing data?
Answer: Missing data can be handled by removing rows, imputing values (mean, median, mode), or using algorithms that support missing data.

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Today, let's understand SQL JOINS in detail: 📝

SQL JOINs are used to combine rows from two or more tables based on related columns.

🟢 1. INNER JOIN
Returns only the matching rows from both tables.

Example:
SELECT Employees.name, Departments.dept_name
FROM Employees
INNER JOIN Departments
ON Employees.dept_id = Departments.id;

📌 Use Case: Employees with assigned departments only.

🔵 2. LEFT JOIN (LEFT OUTER JOIN)
Returns all rows from the left table, and matching rows from the right table. If no match, returns NULL.

Example:
SELECT Employees.name, Departments.dept_name
FROM Employees
LEFT JOIN Departments
ON Employees.dept_id = Departments.id;

📌 Use Case: All employees, even those without a department.

🟠 3. RIGHT JOIN (RIGHT OUTER JOIN)
Returns all rows from the right table, and matching rows from the left table. If no match, returns NULL.

Example:
SELECT Employees.name, Departments.dept_name
FROM Employees
RIGHT JOIN Departments
ON Employees.dept_id = Departments.id;

📌 Use Case: All departments, even those without employees.

🔴 4. FULL OUTER JOIN
Returns all rows from both tables. Non-matching rows show NULL.

Example:
SELECT Employees.name, Departments.dept_name
FROM Employees
FULL OUTER JOIN Departments
ON Employees.dept_id = Departments.id;

📌 Use Case: See all employees and departments, matched or not.

📝 Tips:
⦁ Always specify the join condition (ON)
⦁ Use table aliases to simplify long queries
⦁ NULLs can appear if there's no match in a join

📌 SQL Roadmap: https://whatsapp.com/channel/0029VanC5rODzgT6TiTGoa1v/1506

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📊 Data Analytics Career Paths & What to Learn 🧠📈

🧮 1. Data Analyst
▶️ Tools: Excel, SQL, Power BI, Tableau
▶️ Skills: Data cleaning, data visualization, business metrics
▶️ Languages: Python (Pandas, Matplotlib)
▶️ Projects: Sales dashboards, customer insights, KPI reports

📉 2. Business Analyst
▶️ Tools: Excel, SQL, PowerPoint, Tableau
▶️ Skills: Requirements gathering, stakeholder communication, data storytelling
▶️ Domain: Finance, Retail, Healthcare
▶️ Projects: Market analysis, revenue breakdowns, business forecasts

🧠 3. Data Scientist
▶️ Tools: Python, R, Jupyter, Scikit-learn
▶️ Skills: Statistics, ML models, feature engineering
▶️ Projects: Churn prediction, sentiment analysis, classification models

🧰 4. Data Engineer
▶️ Tools: SQL, Python, Spark, Airflow
▶️ Skills: Data pipelines, ETL, data warehousing
▶️ Platforms: AWS, GCP, Azure
▶️ Projects: Real-time data ingestion, data lake setup

📦 5. Product Analyst
▶️ Tools: Mixpanel, SQL, Excel, Tableau
▶️ Skills: User behavior analysis, A/B testing, retention metrics
▶️ Projects: Feature adoption, funnel analysis, product usage trends

📌 6. Marketing Analyst
▶️ Tools: Google Analytics, Excel, SQL, Looker
▶️ Skills: Campaign tracking, ROI analysis, segmentation
▶️ Projects: Ad performance, customer journey, CLTV analysis

🧪 7. Analytics QA (Data Quality Tester)
▶️ Tools: SQL, Python (Pytest), Excel
▶️ Skills: Data validation, report testing, anomaly detection
▶️ Projects: Dataset audits, test case automation for dashboards

💡 Tip: Pick a role → Learn tools → Practice with real datasets → Build a portfolio → Share insights

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🧠 How much SQL is enough to crack a Data Analyst Interview?

📌 Basic Queries
⦁ SELECT, FROM, WHERE, ORDER BY, LIMIT
⦁ Filtering, sorting, and simple conditions

🔍 Joins & Relations
⦁ INNER JOIN, LEFT JOIN, RIGHT JOIN, FULL JOIN
⦁ Using keys to combine data from multiple tables

📊 Aggregate Functions
⦁ COUNT(), SUM(), AVG(), MIN(), MAX()
⦁ GROUP BY and HAVING for grouped analysis

🧮 Subqueries & CTEs
⦁ SELECT within SELECT
⦁ WITH statements for better readability

📌 Set Operations
⦁ UNION, INTERSECT, EXCEPT
⦁ Merging and comparing result sets

📅 Date & Time Functions
⦁ NOW(), CURDATE(), DATEDIFF(), DATE_ADD()
⦁ Formatting & filtering date columns

🧩 Data Cleaning
⦁ TRIM(), UPPER(), LOWER(), REPLACE()
⦁ Handling NULLs & duplicates

📈 Real World Tasks
⦁ Sales by region
⦁ Weekly/monthly trend tracking
⦁ Customer churn queries
⦁ Product category comparisons

✅ Must-Have Strengths:
⦁ Writing clear, efficient queries
⦁ Understanding data schemas
⦁ Explaining logic behind joins/filters
⦁ Drawing business insights from raw data

SQL Resources: https://whatsapp.com/channel/0029VanC5rODzgT6TiTGoa1v

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📊 Top 5 Data Analysis Techniques You Should Know 🧠📈

1️⃣ Descriptive Analysis
▶️ Summarizes data to understand what happened
▶️ Tools: Mean, median, mode, standard deviation, charts
▶️ Example: Monthly sales report showing total revenue

2️⃣ Diagnostic Analysis
▶️ Explores why something happened
▶️ Tools: Correlation, root cause analysis, drill-downs
▶️ Example: Investigating why customer churn spiked last quarter

3️⃣ Predictive Analysis
▶️ Uses historical data to forecast future trends
▶️ Tools: Regression, time series analysis, machine learning
▶️ Example: Predicting next month's product demand

4️⃣ Prescriptive Analysis
▶️ Recommends actions based on predictions
▶️ Tools: Optimization models, decision trees
▶️ Example: Suggesting optimal inventory levels to reduce costs

5️⃣ Exploratory Data Analysis (EDA)
▶️ Initial investigation to find patterns and anomalies
▶️ Tools: Data visualization, summary statistics, outlier detection
▶️ Example: Visualizing user behavior on a website to identify trends

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Top 50 Data Analyst Interview Questions (2025) 🎯📊

1. What does a data analyst do?
2. Difference between data analyst, data scientist, and data engineer.
3. What are the key skills every data analyst must have?
4. Explain the data analysis process.
5. What is data wrangling or data cleaning?
6. How do you handle missing values?
7. What is the difference between structured and unstructured data?
8. How do you remove duplicates in a dataset?
9. What are the most common data types in Python or SQL?
10. What is the difference between INNER JOIN and LEFT JOIN?
11. Explain the concept of normalization in databases.
12. What are measures of central tendency?
13. What is standard deviation and why is it important?
14. Difference between variance and covariance.
15. What are outliers and how do you treat them?
16. What is hypothesis testing?
17. Explain p-value in simple terms.
18. What is correlation vs. causation?
19. How do you explain insights from a dashboard to non-technical stakeholders?
20. What tools do you use for data visualization?
21. Difference between Tableau and Power BI.
22. What is a pivot table?
23. How do you build a dashboard from scratch?
49. What do you do if data contradicts business intuition?
50. What are your favorite analytics tools and why?

🎓 Data Analyst Jobs:
https://whatsapp.com/channel/0029Vaxjq5a4dTnKNrdeiZ0J

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SQL Interviews LOVE to test you on Window Functions. Here’s the list of 7 most popular window functions

👇 𝟕 𝐌𝐨𝐬𝐭 𝐓𝐞𝐬𝐭𝐞𝐝 𝐖𝐢𝐧𝐝𝐨𝐰 𝐅𝐮𝐧𝐜𝐭𝐢𝐨𝐧𝐬

* RANK() - gives a rank to each row in a partition based on a specified column or value

* DENSE_RANK() - gives a rank to each row, but DOESN'T skip rank values

* ROW_NUMBER() - gives a unique integer to each row in a partition based on the order of the rows

* LEAD() - retrieves a value from a subsequent row in a partition based on a specified column or expression

* LAG() - retrieves a value from a previous row in a partition based on a specified column or expression

* NTH_VALUE() - retrieves the nth value in a partition

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✅ SQL Window Functions – Part 1: 🧠

What Are Window Functions?
They perform calculations across rows related to the current row without reducing the result set. Common for rankings, comparisons, and totals.

1. RANK()
Assigns a rank based on order. Ties get the same rank, but next rank is skipped.

Syntax:
RANK() OVER (
PARTITION BY column
ORDER BY column
)
Example Table: Sales
| Employee | Region | Sales |
|----------|--------|-------|
| A | East | 500 |
| B | East | 600 |
| C | East | 600 |
| D | East | 400 |

Query:
SELECT Employee, Sales,
RANK() OVER (PARTITION BY Region ORDER BY Sales DESC) AS Rank
FROM Sales;

Result:
| Employee | Sales | Rank |
|----------|-------|------|
| B | 600 | 1 |
| C | 600 | 1 |
| A | 500 | 3 |
| D | 400 | 4 |

2. DENSE_RANK()
Same logic as RANK but does not skip ranks.

Query:
SELECT Employee, Sales,
DENSE_RANK() OVER (PARTITION BY Region ORDER BY Sales DESC) AS DenseRank
FROM Sales;

Result:
| Employee | Sales | DenseRank |
|----------|-------|-----------|
| B | 600 | 1 |
| C | 600 | 1 |
| A | 500 | 2 |
| D | 400 | 3 |

RANK vs DENSE_RANK
- RANK skips ranks after ties. Tie at 1 means next is 3
- DENSE_RANK does not skip. Tie at 1 means next is 2

💡 Use RANK when position gaps matter
💡 Use DENSE_RANK for continuous ranking

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🌐 Data Analytics Tools & Their Use Cases 📊📈

🔹 Excel ➜ Spreadsheet analysis, pivot tables, and basic data visualization
🔹 SQL ➜ Querying databases for data extraction and relational analysis
🔹 Tableau ➜ Interactive dashboards and storytelling with visual analytics
🔹 Power BI ➜ Business intelligence reporting and real-time data insights
🔹 Google Analytics ➜ Web traffic analysis and user behavior tracking
🔹 Python (with Pandas) ➜ Data manipulation, cleaning, and exploratory analysis
🔹 R ➜ Statistical computing and advanced graphical visualizations
🔹 Apache Spark ➜ Big data processing for distributed analytics workloads
🔹 Looker ➜ Semantic modeling and embedded analytics for teams
🔹 Alteryx ➜ Data blending, predictive modeling, and workflow automation
🔹 Knime ➜ Visual data pipelines for no-code analytics and ML
🔹 Splunk ➜ Log analysis and real-time operational intelligence

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📊 𝗜𝗻𝘁𝗲𝗿𝘃𝗶𝗲𝘄𝗲𝗿: How do you create a running total in SQL?

👋 𝗠𝗲 Use the WINDOW FUNCTION with OVER() clause:

  Date,
  Amount,
  SUM(Amount) OVER (ORDER BY Date) AS RunningTotal
FROM Sales;

🧠 Logic Breakdown: 
- SUM(Amount) → Aggregates the values 
- OVER(ORDER BY Date) → Maintains order for accumulation 
- No GROUP BY needed 

✅ Use Case: Track cumulative revenue, expenses, or orders by date

💡 SQL Tip:
Add PARTITION BY in OVER() if you want running totals by category or region.

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📊 𝗜𝗻𝘁𝗲𝗿𝘃𝗶𝗲𝘄𝗲𝗿: How do you get the 2nd highest salary in SQL?

👋 𝗠𝗲: Use ORDER BY with LIMIT or OFFSET, or a subquery.

MySQL / PostgreSQL (with LIMIT & OFFSET):

SELECT salary  
FROM employees  
ORDER BY salary DESC  
LIMIT 1 OFFSET 1;

Using Subquery (Works on most databases):

SELECT MAX(salary)  
FROM employees  
WHERE salary < (SELECT MAX(salary) FROM employees);

🧠 Logic Breakdown:
- First method sorts and skips the top result
- Second method finds the highest salary below the max

💡 Tip: Use DENSE_RANK() if multiple employees share the same salary rank

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✅ SQL Checklist for Data Analysts 🧠💻

📚 1. Understand SQL Basics
☑ What is SQL and how databases work
☑ Relational vs non-relational databases
☑ Table structure: rows, columns, keys

🧩 2. Core SQL Queries
☑ SELECT, FROM, WHERE
☑ ORDER BY, LIMIT
☑ DISTINCT, BETWEEN, IN, LIKE

🔗 3. Master Joins
☑ INNER JOIN
☑ LEFT JOIN / RIGHT JOIN
☑ FULL OUTER JOIN
☑ Practice combining data from multiple tables

📊 4. Aggregation & Grouping
☑ COUNT, SUM, AVG, MIN, MAX
☑ GROUP BY & HAVING
☑ Aggregate filtering

📈 5. Subqueries & CTEs
☑ Use subqueries inside SELECT/WHERE
☑ WITH clause for common table expressions
☑ Nested queries and optimization basics

🧮 6. Window Functions
☑ RANK(), ROW_NUMBER(), DENSE_RANK()
☑ PARTITION BY & ORDER BY
☑ LEAD(), LAG(), SUM() OVER

🧹 7. Data Cleaning with SQL
☑ Remove duplicates (DISTINCT, ROW_NUMBER)
☑ Handle NULLs
☑ Use CASE WHEN for conditional logic

🛠️ 8. Practice & Real Tasks
☑ Write queries from real datasets
☑ Analyze sales, customers, transactions
☑ Build reports with JOINs and aggregations

📁 9. Tools to Use
☑ PostgreSQL / MySQL / SQL Server
☑ db-fiddle, Mode Analytics, DataCamp, StrataScratch
☑ VS Code + SQL extensions

🚀 10. Interview Prep
☑ Practice 50+ SQL questions
☑ Solve problems on LeetCode, HackerRank
☑ Explain query logic clearly in mock interviews

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