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✅ Top Power BI Interview Questions with Answers: Part-3 🧠

21. What are custom visuals in Power BI? 🎨
Custom visuals are user-created or third-party visuals beyond the default ones in Power BI (e.g., Sankey charts, heat maps). They can be downloaded from Microsoft AppSource or imported via .pbiviz files to meet specific business visualization needs.

22. How do you optimize Power BI performance? ⚡
- Use star schema for modeling
- Remove unused columns
- Reduce cardinality
- Prefer Import mode over DirectQuery (if possible)
- Use variables in DAX to avoid repeated calculations
- Disable auto date/time in load options
- Avoid bi-directional relationships unless necessary

23. What is the difference between ALL and ALLEXCEPT in DAX? ↔️
- ALL() removes filters from all columns or a table.
- ALLEXCEPT() removes filters from all columns except the specified ones.
Example:

CALCULATE(SUM(Sales), ALL(Region)) 
-- Ignores Region filter

CALCULATE(SUM(Sales), ALLEXCEPT(Sales, Product)) 
-- Ignores all filters except Product

24. What is the CALCULATE function in DAX? 🧮
CALCULATE() modifies the context of a calculation by applying filters. It’s used to create dynamic measures.
Example:

Sales_North = CALCULATE(SUM(Sales[Amount]), Region = "North")

25. What is the difference between SUMX and SUM? ➕
- SUM() adds up a single column.
- SUMX() adds up the result of a row-wise expression.
Example:

SUM(Sales[Revenue])  
SUMX(Sales, Sales[Quantity] * Sales[Price])

26. How do you handle null or blank values in Power BI? 🚫
Use DAX functions:
- IF(ISBLANK([Column]), "N/A", [Column])
- COALESCE([Column], 0)
You can also filter or replace blanks using Power Query.

27. What is the RELATED function in DAX? 🔗
RELATED() fetches values from a related table based on relationships.
Example:

RELATED(Product[Category]) 
-- Gets category name from related Product table

28. What is a star schema vs snowflake schema? ⭐❄️
- Star schema: Central fact table with denormalized dimension tables.
- Snowflake schema: Dimension tables are normalized (broken into sub-tables).
Star schema is preferred in Power BI for simplicity and performance.

29. What is Power BI Embedded? 🌐
Power BI Embedded is a Microsoft Azure service that allows developers to embed interactive Power BI visuals and reports into custom applications (web/apps) using APIs and SDKs.

30. What are KPIs and how do you create them? 🎯
KPIs (Key Performance Indicators) are metrics that track performance against goals. In Power BI, you can create KPIs using measures and visuals like KPI cards or conditional formatting based on thresholds.
Example: Sales vs Target with colored indicators.

💬 Double Tap ♥️ For Part-4

Top Power BI Interview Questions with Answers: Part-2 🧠

11. What is a dashboard vs a report?
• Report: A multi-page, detailed view of your data with multiple visuals per page. Built in Power BI Desktop.
• Dashboard: A single-page summary of visuals pinned from reports. Created in Power BI Service.

12. How do you publish a report to the Power BI Service?
• Click Publish in Power BI Desktop → Sign in → Select your workspace.
• The report uploads to Power BI Service for sharing, scheduling, and dashboard creation.

13. What is Power BI Gateway?
• A bridge between on-premises data and the Power BI Service.
• Two types:
– Personal Gateway (for individual use)
– Standard Gateway (for team/shared use)

14. Explain row-level security in Power BI
• Limits data visibility for users based on roles.
• You define roles with DAX filters (e.g., Region = "West") in Desktop, then assign users to roles in Service.

15. What is a bookmark?
• Saves the current state of a report page (filters, visuals, selections).
• Useful for navigation, storytelling, or toggling views.

16. How do you schedule data refresh in Power BI?
• In Power BI Service:
– Go to the dataset → Schedule refresh
• Set frequency, time, and configure credentials if needed (Gateway required for on-prem data).

17. What are visuals in Power BI?
• Graphical representations of data (bar charts, line graphs, maps, cards, etc.).
• Custom visuals can also be imported for advanced scenarios.

18. How can you import data into Power BI?
• Use Get Data → choose sources: Excel, SQL Server, Web, APIs, etc.
• Data is then transformed via Power Query and loaded into the model.

19. What is the difference between DirectQuery and Import mode?
• Import: Data is cached into Power BI → Faster but requires refreshes.
• DirectQuery: Queries data live from the source → Slower, but always current.

20. What is drillthrough and drilldown?
• Drillthrough: Navigate to a new page filtered by selected value (e.g., click a region → open region detail page).
• Drilldown: Explore data hierarchy within the same visual (e.g., year → quarter → month).

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Top Power BI Interview Questions with Answers: Part-1 🧠

1️⃣ What is Power BI?
Power BI is a business analytics tool by Microsoft that allows users to visualize data, build interactive reports, and gain insights. It connects to various data sources, transforms raw data, and helps in decision-making through real-time dashboards and reports.

2️⃣ Difference between Power BI Desktop and Power BI Service
Power BI Desktop: A Windows application used for building and designing reports. It allows data import, modeling, and creating visuals.
Power BI Service: A cloud-based platform where reports/dashboards can be published, shared, and accessed online. It supports collaboration, scheduled refresh, and sharing.

3️⃣ What are the main components of Power BI?
• Power BI Desktop – For report development
• Power BI Service – Online sharing and collaboration
• Power BI Mobile – Mobile access to reports
• Power Query – Data transformation
• Power Pivot – Data modeling
• Power View – Data visualization
• Power Map – Geo-spatial visualization

4️⃣ What is Power Query?
Power Query is a data connection and transformation tool used in Power BI to import, clean, and reshape data from various sources before loading it into the model. It uses the M language and provides a no-code editor for ETL operations.

5️⃣ What is DAX in Power BI?
DAX (Data Analysis Expressions) is a formula language used in Power BI for creating custom calculations, measures, and calculated columns. It is essential for data modeling and creating business logic inside the report.

6️⃣ What are measures and calculated columns?
Measures: Calculations evaluated at query time (e.g., SUM of sales). Created using DAX. Used in visuals.
Calculated Columns: New data columns added to tables. Evaluated during data load or refresh. Used for data transformation.

7️⃣ How do you create relationships between tables?
Relationships are created in the Model view by dragging one column (usually a key) to a matching column in another table. You can also define them manually by selecting:
• Primary foreign keys
• Cardinality (One-to-One, One-to-Many)
• Cross-filter direction (Single/Both)

8️⃣ What is a data model?
A data model is the structured combination of tables, relationships, and business logic (DAX measures, calculated columns) within Power BI that defines how data is stored, connected, and queried for reporting.

9️⃣ What are slicers in Power BI?
Slicers are visual filters in Power BI reports that allow users to select values and dynamically filter other visuals. They provide an intuitive way to control which data is displayed (e.g., filter by year or region).

🔟 Difference between slicers and filters
Slicers: Visual elements placed on reports; end-users can interact with them. Visible on the report page.
Filters: Applied in the filter pane (visual-level, page-level, report-level); not always visible to users.

Double Tap ♥️ For Part-2

✅ Top 50 Power BI Interview Questions 📊💼

1. What is Power BI?
2. Difference between Power BI Desktop and Power BI Service
3. What are the main components of Power BI?
4. What is Power Query?
5. What is DAX in Power BI?
6. What are measures and calculated columns?
7. How do you create relationships between tables?
8. What is a data model?
9. What are slicers in Power BI?
10. Difference between slicers and filters
11. What is a dashboard vs a report?
12. How do you publish a report to the Power BI Service?
13. What is Power BI Gateway?
14. Explain row-level security in Power BI
15. What is a bookmark?
16. How do you schedule data refresh in Power BI?
17. What are visuals in Power BI?
18. How can you import data into Power BI?
19. What is the difference between DirectQuery and Import mode?
20. What is drillthrough and drilldown?
21. What are custom visuals in Power BI?
22. How do you optimize Power BI performance?
23. What is the difference between ALL and ALLEXCEPT in DAX?
24. What is the CALCULATE function in DAX?
25. What is the difference between SUMX and SUM?
26. How do you handle null or blank values in Power BI?
27. What is the RELATED function in DAX?
28. What is a star schema vs snowflake schema?
29. What is Power BI Embedded?
30. What are KPIs and how do you create them?
31. What are tooltips in Power BI?
32. How do you use variables in DAX?
33. What are quick measures?
34. What is the use of FORMAT() in DAX?
35. What is a calculated table?
36. How do you apply conditional formatting in visuals?
37. What are the different types of filters in Power BI?
38. What is a hierarchy in Power BI?
39. How does Power BI handle large datasets?
40. What is Incremental Refresh?
41. How do you share reports securely in Power BI?
42. What are Dataflows in Power BI?
43. What is Q&A in Power BI?
44. What is the DAX function EARLIER() used for?
45. What is the significance of context in DAX?
46. What are parameters in Power BI?
47. What is drillthrough vs drilldown vs drill up?
48. What is report-level filter vs visual-level filter?
49. How do you export data from Power BI?
50. Explain a Power BI project you’ve worked on.

💬 Tap ❤️ for the detailed answers!

✅ Power BI Basics You Should Know 📊⚡

1️⃣ What is Power BI?
A Microsoft tool for data visualization and business intelligence. It helps turn raw data into interactive dashboards and reports.

2️⃣ Key Components:
• Power BI Desktop: For building reports
• Power BI Service: Online sharing collaboration
• Power BI Mobile: View reports on phones/tablets
• Power Query: Data transformation tool
• DAX: Formula language for calculations

3️⃣ Common Visuals:
• Bar/Column Charts
• Pie Charts
• Line Charts
• Maps
• Slicers Filters

4️⃣ Data Sources You Can Connect:
• Excel, SQL Server, SharePoint, Google Sheets, Web APIs, etc.

5️⃣ Important Concepts:
• Measures (calculated on the fly)
• Calculated Columns (stored in data)
• Relationships (connecting tables)
• Data Model (behind-the-scenes logic)

6️⃣ Sharing Options:
• Publish to Power BI Service
• Export to PDF
• Embed in apps or websites

💡 Pro Tip: Master DAX and data modeling to build truly powerful dashboards.

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✅ Power BI DAX Basics 📊🧠

DAX (Data Analysis Expressions) is Power BI's formula language for custom calculations, measures, and columns—essential for dynamic insights in 2025 reports.

1️⃣ SUM()
Adds column values.
Example: Total Sales = SUM(Sales[Amount])

2️⃣ AVERAGE()
Gets column average.
Example: Avg Salary = AVERAGE(Employee[Salary])

3️⃣ COUNT(), COUNTA(), COUNTROWS()
⦁ COUNT() for numerics
⦁ COUNTA() for non-blanks
⦁ COUNTROWS() for table rows
Examples: Total Orders = COUNT(Orders[OrderID]) | Total Customers = COUNTROWS(Customers)

4️⃣ CALCULATE()
Modifies calculation context (DAX's powerhouse).
Example: Sales East = CALCULATE(SUM(Sales[Amount]), Sales[Region] = "East")

5️⃣ FILTER()
Builds filtered tables for CALCULATE.
Example: High Sales = CALCULATE(SUM(Sales[Amount]), FILTER(Sales, Sales[Amount] > 1000))

6️⃣ IF()
Adds conditional logic.
Example: Sales Category = IF(Sales[Amount] > 500, "High", "Low")

7️⃣ SWITCH()
Handles multiple conditions cleanly.
Example: Rating = SWITCH(TRUE(), [Score] >= 90, "A", [Score] >= 75, "B", [Score] >= 60, "C", "Fail")

8️⃣ ALL()
Removes filters for totals.
Example: % of Total = DIVIDE(SUM(Sales[Amount]), CALCULATE(SUM(Sales[Amount]), ALL(Sales)))

9️⃣ DISTINCT()
Gets unique column values.
Example: Unique Products = DISTINCT(Sales[Product])

🔟 Measures vs Calculated Columns
⦁ Measures: Dynamic, context-based (best for visuals)
⦁ Calculated Columns: Row-by-row, stored (use sparingly for performance)

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