Prepare for your Power BI interview with this comprehensive guide featuring 30 essential questions and answers. Covering basic, intermediate, and advanced topics, this post is designed for freshers, candidates with 1-3 years of experience, and professionals with 3-6 years in Power BI development and analytics.
Basic Power BI Interview Questions
1. What is Power BI?
Power BI is a business analytics tool that enables users to visualize and share insights from data through interactive dashboards and reports. It combines data connectivity, transformation, modeling, and visualization capabilities in a single platform.
2. What are the main components of Power BI?
The main components include Power BI Desktop for report creation, Power BI Service for sharing and collaboration, Power BI Mobile for access on devices, and Power BI Gateway for on-premises data connectivity.
3. What is Power Query in Power BI?
Power Query is the data transformation and preparation engine in Power BI. It allows users to connect to data sources, clean, reshape, and transform data before loading it into the data model.
4. What is Power Pivot in Power BI?
Power Pivot is the data modeling component that handles complex data relationships, calculations using DAX, and in-memory processing with the xVelocity engine for fast analytics.
5. What is DAX in Power BI?
DAX stands for Data Analysis Expressions. It is a formula language used to create calculated columns, measures, and custom tables for advanced data analysis in Power BI data models.
6. What are the different types of charts available in Power BI?
Common chart types include bar and column charts for comparisons, line and area charts for trends, pie and donut charts for proportions, tables and matrices for detailed data, scatter and bubble charts for relationships, maps for geographical data, and funnel charts for process stages.
7. How do you connect to data sources in Power BI?
In Power BI Desktop, click Get Data, select from options like Excel, SQL Server, web, or folders, authenticate, and load or transform the data using Power Query Editor.
8. What is the difference between a measure and a calculated column in Power BI?
A calculated column is computed row-by-row during data refresh and stored in the model. A measure is calculated dynamically at query time based on filter context and is not stored.
9. What are filters in Power BI?
Filters control data displayed in visuals and include visual-level filters for single visuals, page-level for entire pages, report-level for all pages, and drill-through filters for detailed navigation.
10. What is a slicer in Power BI?
A slicer is an on-canvas filter visual that allows users to interactively filter data in reports by selecting values from lists, dates, or hierarchies.
Intermediate Power BI Interview Questions
11. How do you publish a Power BI report to Power BI Service?
Open the report in Power BI Desktop, click Publish, select the workspace in Power BI Service, and confirm. The report and dataset appear in the online workspace for sharing.
12. What are the differences between Power BI Desktop and Power BI Service?
Power BI Desktop is for creating reports and data models locally. Power BI Service is cloud-based for collaboration, sharing dashboards, scheduling refreshes, and consuming content.
13. How do you handle missing data in Power BI?
Use Power Query to replace missing values with zeros, averages, or custom text, remove rows with errors, or fill down/up values. For dates, create custom date tables to fill gaps.
14. What is Row-Level Security (RLS) in Power BI?
RLS restricts data access at the row level based on user roles. Implement it by creating DAX expressions in the data model that filter rows dynamically for specific users or groups.
15. Explain query folding in Power BI.
Query folding pushes transformation steps back to the data source as native SQL queries, improving performance by processing data at the source instead of in Power BI.
16. What is the M language in Power BI?
M is the functional, case-sensitive scripting language used in Power Query for advanced data transformations, custom functions, and complex ETL operations.
17. How do you create relationships between tables in Power BI?
In Model view, drag primary key from one table to foreign key in another. Choose cardinality (one-to-many), cross-filter direction, and active/inactive status.
18. What is a gateway in Power BI?
The Power BI Gateway is software that connects on-premises data sources to Power BI Service, enabling secure data refresh without moving data to the cloud.
19. Give an example of a DAX measure for total sales.
Total Sales = SUM(Sales[Amount])20. What is the CALCULATE function in DAX?
CALCULATE modifies the filter context for an expression. It applies filters specified as arguments, enabling dynamic calculations like year-over-year growth.
Advanced Power BI Interview Questions
21. How do you optimize Power BI report performance?
Reduce data by filtering early, remove unused columns, use aggregations, simplify DAX with variables, prefer import mode over DirectQuery, and use Performance Analyzer.
22. What are custom visuals in Power BI?
Custom visuals are third-party or user-developed charts imported from AppSource, extending native visuals like heat maps, word clouds, or advanced gauges.
23. Explain the ALL function in DAX.
ALL removes filters from a table or column, returning all values regardless of current filter context. Used in measures like percentage of total calculations.
24. Scenario: At Zoho, sales data from multiple regions loads slowly. How would you improve it?
Aggregate data at source, enable query folding, create summary tables, remove unused fields in Power Query, and switch to import mode with scheduled refresh.
25. What is DirectQuery mode in Power BI?
DirectQuery queries the data source live without importing data, suitable for real-time needs but slower than import mode and limited in visuals.
26. Scenario: Oracle database has inconsistent date formats across tables. How to merge in Power BI?
In Power Query, standardize formats using Locale and Date.FromText functions, merge queries on common keys, and expand required columns.
27. What are iterator functions in DAX? Give an example.
Iterator functions like SUMX row-iterate over tables applying expressions. Example:
Average Sales per Product = AVERAGEX(Products, SUM(Sales[Amount]))28. Scenario: Salesforce reports need user-specific views at Atlassian. Implement security.
Define RLS roles with DAX like [Region] = USERPRINCIPALNAME(), test in Desktop, publish, and assign users to roles in Power BI Service.
29. How does the USERELATIONSHIP function work?
USERELATIONSHIP activates an inactive relationship for a specific DAX calculation, allowing multiple relationships on the same columns.
30. Scenario: Paytm has 100M+ transaction records. How to analyze in Power BI?
Use aggregations for summaries, incremental refresh partitioning, composite models mixing import/DirectQuery, optimize star schema, and disable auto date/time.
## Key Citations
– [YouTube Top 10 Questions][1]
– [GeeksforGeeks Power BI Q&A][2]
– [DataCamp 45 Essential Questions][3]
– [XelPlus 50 Questions][4]
– [Simplilearn Top 60 Questions][5]
– [YouTube 50 Questions][6]
