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Power BI Interview Questions for Data Analysts 2026
40+ Power BI questions on DAX, Power Query, data modelling, visuals and RLS — with detailed answers and a free PDF cheat sheet.
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Power BI Interview Questions: Basics and Core Concepts
These Power BI interview questions cover everything from foundational concepts to advanced DAX, data modelling, and deployment — giving you a complete preparation guide for 2026. Power BI is a Microsoft business analytics tool widely used in data analyst roles across India, and mastering these questions will help you stand out in technical interviews.
Q1. What is Power BI and what are its main components?
Power BI is a Microsoft business analytics tool. Components: Desktop (report authoring), Service (cloud publishing/sharing), Mobile (iOS/Android apps), Gateway (on-premise data bridge), Report Server (on-premise hosting).
Q2. Difference between Power BI Desktop and Power BI Service?
Desktop: free Windows app for building reports, modelling data, writing DAX. Service: cloud portal (app.powerbi.com) for publishing, sharing, scheduling refreshes, collaboration. Desktop = develop; Service = distribute.
DAX Fundamentals
Q3. What is DAX? Name commonly used functions.
DAX (Data Analysis Expressions) is Power BI's formula language for calculated columns, measures, and tables. Key functions: SUM, AVERAGE, COUNT, CALCULATE, FILTER, ALL, IF, SWITCH, DATEADD, TOTALYTD, SAMEPERIODLASTYEAR, CONCATENATE, FORMAT.
Q4. Calculated column vs measure — difference?
Calculated Column: row-by-row computation at refresh; stored in model; uses row context. Measure: computed dynamically at query time; not stored; uses filter context. Always prefer measures for aggregations — better performance, smaller model.
Q5. Explain CALCULATE() with example.
CALCULATE() evaluates an expression in modified filter context. Example:
Sales_Mumbai = CALCULATE(SUM(Sales[Amount]), Sales[City]="Mumbai") — returns total sales for Mumbai regardless of other report filters.Q6. Row context vs filter context?
Row context: exists inside calculated columns and iterator functions (SUMX, AVERAGEX); references one row at a time. Filter context: exists in measures; determined by slicers, filters, visuals. CALCULATE can transition row to filter context.
Q7. What does ALL() do?
ALL() removes all filters from a table or column. Common use — % of total:
% Total = DIVIDE(SUM(Sales[Amount]), CALCULATE(SUM(Sales[Amount]), ALL(Sales)))Data Modelling
Q8. Star schema vs snowflake schema?
Star: central fact table + flat dimension tables. Simple, fast — recommended for Power BI. Snowflake: normalised dimensions into sub-tables. More joins, slower. Always prefer star schema in Power BI for performance.
Q9. Types of relationships in Power BI?
One-to-Many (1:* — most common), Many-to-One (*:1), One-to-One (1:1 — avoid), Many-to-Many (*:* — needs bridge table). Cross-filter direction: Single (default) or Both (use carefully).
Q10. DirectQuery vs Import mode?
Import: data loaded into memory; fast queries; max ~1 GB compressed; scheduled refresh. DirectQuery: queries sent live to source; always current; slower; no size limit. Use Import for performance, DirectQuery for real-time.
Power Query & Advanced
Q11. What is Power Query and M Language?
Power Query is the data transformation engine in Power BI. M Language is its underlying functional language. Common ops: merge, append, pivot, unpivot, split columns, replace values, conditional columns.
Q12. How do you handle NULL values?
Power Query: Replace Values or Fill Down/Up. DAX:
IF(ISBLANK([Col]), 0, [Col]) or COALESCE([Col], 0). Measures automatically ignore blank rows in most aggregations.Q13. What is Row-Level Security (RLS)?
RLS restricts data access per user. Define DAX filter rules in Desktop (e.g.,
[Region] = USERNAME()), assign users to roles in Service. Users only see their permitted data.Q14. What are bookmarks?
Bookmarks capture report page state (filters, visuals, slicers). Used for: interactive storytelling, toggle views, simulate drill-through, presentation-style report flow.
Q15. What is a Power BI Gateway?
Software on on-premise server allowing Power BI Service to securely access on-premise data for scheduled refresh and DirectQuery. Modes: Personal (single user) and Enterprise/Standard (shared).
💡 Pro Tip: Always use measures instead of calculated columns for aggregations — measures compute on-the-fly and keep model size small.
Related Free Resources
Frequently Asked Questions
Is Power BI free?
Desktop is free. Service has a free tier. Power BI Pro (₹750/user/month) is needed for sharing. Power BI Premium offers dedicated capacity for enterprises.
Power BI vs Tableau?
Power BI: Microsoft ecosystem, DAX/M, affordable, great for Excel users. Tableau: Salesforce, VizQL, superior visualisation flexibility, more expensive. Power BI dominates the Indian job market for analytics roles.
Do I need SQL for Power BI?
Not mandatory but strongly recommended. SQL helps write native queries in Power Query, understand data models, and write more efficient DAX. Most data analyst jobs expect both Power BI and SQL.
Power BI salary in India?
Entry-level: ₹4–6 LPA. Mid-level (2–4 yrs): ₹8–14 LPA. Senior Power BI developers/architects: ₹18–30+ LPA depending on domain and company.
What is the PL-300 certification?
PL-300 (Microsoft Power BI Data Analyst) is the official Microsoft certification. Covers data preparation, modelling, visualisation, and deployment. Widely recognised and adds significant value to your resume.
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