Prepare for your Power BI interview with this comprehensive guide featuring 30 essential questions and answers. These cover conceptual, practical, and scenario-based topics, progressing from basic to advanced difficulty, suitable for freshers, candidates with 1-3 years experience, and those with 3-6 years.
Basic Power BI Interview Questions
1. What is Power BI?
Power BI is a business analytics tool by Microsoft that enables users to visualize and share insights from data through interactive reports and dashboards.
2. What are the key 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 the difference between Power BI Desktop and Power BI Service?
Power BI Desktop is a free Windows application for creating reports and data models, while Power BI Service is a cloud-based platform for publishing, sharing, and managing reports.
4. Name some common visualizations available in Power BI.
Common visualizations 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, and maps for geographical data.
5. 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 a list, dropdown, or date range.
6. How do you connect to a data source in Power BI Desktop?
In Power BI Desktop, click “Get Data” from the Home tab, select the data source type like Excel or SQL Server, provide connection details, and load or transform the data using Power Query.
7. What are the different types of filters in Power BI?
Filters include visual-level filters for specific visuals, page-level filters for all visuals on a page, report-level filters for the entire report, and drill-through filters for detailed navigation.
8. What is Power Query in Power BI?
Power Query is the data transformation and preparation engine in Power BI used to clean, reshape, and combine data from multiple sources before loading it into the data model.
9. Explain Import mode versus DirectQuery in Power BI.
Import mode loads a snapshot of data into Power BI for fast performance, while DirectQuery queries the source database live without storing data locally, suitable for large or real-time datasets.
10. How do you publish a report from Power BI Desktop to Power BI Service?
Open the report in Power BI Desktop, click “Publish” in the Home tab, select the workspace in Power BI Service, and confirm to upload the report and dataset.
Intermediate Power BI Interview Questions
11. What is DAX in Power BI?
DAX (Data Analysis Expressions) is a formula language used in Power BI to create calculated columns, measures, and tables for advanced data analysis and calculations.
12. What is the difference between a measure and a calculated column in Power BI?
A calculated column is computed row-by-row at data load time and stored in the model, while a measure is calculated dynamically at query time based on report filters and context.
13. Provide an example of a DAX measure for total sales.
Total Sales = SUM(Sales[Amount])
Total Sales = SUM(Sales[Amount])14. What is the CALCULATE function in DAX?
CALCULATE modifies the filter context of an expression, allowing you to apply specific filters or remove existing ones for more flexible calculations.
15. How do you handle missing data in Power BI?
Handle missing data by using Power Query to fill values with defaults like zeros or averages, filter out nulls, or replace them based on business logic before loading.
16. Explain relationships in Power BI data models.
Relationships connect tables in the data model using common keys, enabling cross-table filtering and calculations; they can be one-to-many, many-to-one, or one-to-one.
17. What is Row-Level Security (RLS) in Power BI?
RLS restricts data access at the row level based on user roles, implemented via DAX filters in the data model to show only relevant data to authorized users.
18. How do you implement RLS in Power BI?
Create roles in Power BI Desktop under Modeling tab, define DAX filters like [Region] = USERPRINCIPALNAME(), assign users to roles, and publish to enforce in Power BI Service.
19. What is the ALL function in DAX?
ALL removes filters from specified columns or tables, returning all values regardless of current filter context, often used in measures for totals.
20. How do you optimize Power BI report performance?
Optimize by reducing data volume with filters, removing unused columns, using aggregations, simplifying DAX, preferring Import mode, and running Performance Analyzer.
Advanced Power BI Interview Questions
21. In a Zoho project, how would you combine multiple data sources with different structures into one Power BI report?
Use Power Query to append or merge queries after transforming columns to match data types, then create relationships in the model for unified analysis.
22. What are iterator functions in DAX? Give an example.
Iterator functions like SUMX iterate over a table row-by-row applying an expression; example: SUMX(Sales, Sales[Quantity] * Sales[UnitPrice]).
23. Explain USERELATIONSHIP function in DAX.
USERELATIONSHIP activates an inactive relationship for a specific calculation, allowing multiple date tables or alternate paths in complex models.
24. How would you track live updates from a Salesforce database in a Power BI report?
Configure DirectQuery mode to the Salesforce source and set up scheduled refreshes or use real-time streaming datasets for live updates.
25. For a Paytm scenario with large sales data, how do you identify outliers?
Create a measure using DAX like Outliers = IF(ABS(Sales[Amount] – AVERAGE(Sales[Amount])) > 2 * STDEV.P(Sales[Amount]), Sales[Amount], BLANK()), then visualize with scatter plots.
26. What are What-If parameters in Power BI?
What-If parameters allow users to simulate scenarios by adjusting input values like sliders, creating dynamic measures that respond to changes.
27. How do you set up data refresh in Power BI Service for an Oracle on-premises database?
Install and configure On-premises Data Gateway, connect it to the dataset in Power BI Service, and schedule refreshes up to 8 times daily.
28. In an Adobe analytics scenario, your report shows different views based on user clicks. How do you achieve this?
Use bookmarks to capture visual states, add buttons linked to bookmarks, or leverage drill-through pages for interactive navigation.
29. For aggregating 100 million records from an SAP database in Power BI, what approach do you take?
Use aggregations in the model for summary tables, apply query folding in Power Query, enable incremental refresh, and composite models with DirectQuery for details.
30. How do you avoid circular dependencies in DAX expressions?
Avoid circular dependencies by not referencing measures or columns that depend on each other mutually; use CALCULATE carefully and prefer variables for intermediate calculations.
