Power BI is now the most-demanded BI tool across TCS, Infosys, Wipro, Cognizant, Capgemini, and HCL. From freshers to senior BI developers, Power BI questions come up in almost every data-related interview round in 2026.
This guide compiles the most-asked Power BI questions at major Indian IT companies with interview-ready answers covering DAX, data modelling, report design, and performance optimization.
Interview Tip: At TCS, Infosys and Wipro, Power BI questions are usually in the Technical Round 1 or Technical Round 2. They test both conceptual understanding AND hands-on experience. Always back your answers with a real project example.
📗 Basic Power BI Questions (Fresher / 1-2 Years)
Q1 — TCS, Infosys
What is the difference between a Measure and a Calculated Column in Power BI?
Model Answer
Calculated Column: Computed row-by-row during data refresh and stored in the model. Evaluated in the context of each row. Uses more memory. Best for row-level filtering, relationships, or text-based calculations.
Measure: Calculated dynamically at query time based on the current filter context. Not stored in the model. Uses less memory. Best for aggregations (SUM, AVG, COUNT) shown in visuals.
Measure: Calculated dynamically at query time based on the current filter context. Not stored in the model. Uses less memory. Best for aggregations (SUM, AVG, COUNT) shown in visuals.
-- Calculated Column (Row Context)
Profit = Sales[Revenue] - Sales[Cost]
-- Measure (Filter Context)
Total Profit = SUM(Sales[Profit])
Q2 — Wipro, Capgemini
What are the different types of filters in Power BI?
Model Answer
Power BI has 4 types of filters:
1. Visual-level filters — Apply only to one specific visual
2. Page-level filters — Apply to all visuals on a specific page
3. Report-level filters — Apply to all pages in the report
4. Drillthrough filters — Pass filter context from one page to another for detail view
Plus, Row-Level Security (RLS) filters data at the model level based on user identity.
1. Visual-level filters — Apply only to one specific visual
2. Page-level filters — Apply to all visuals on a specific page
3. Report-level filters — Apply to all pages in the report
4. Drillthrough filters — Pass filter context from one page to another for detail view
Plus, Row-Level Security (RLS) filters data at the model level based on user identity.
Q3 — TCS
What is a Star Schema? Why is it preferred in Power BI?
Model Answer
A Star Schema is a data modelling pattern with one central Fact Table (containing measures like Sales Amount, Quantity) connected to multiple Dimension Tables (Date, Product, Customer, Region).
It's preferred in Power BI because:
• Simpler DAX formulas — filter context flows naturally from dimensions to facts
• Faster query performance (VertiPaq engine optimized for star schemas)
• Easier to understand and maintain
• Better compression compared to denormalized flat tables
It's preferred in Power BI because:
• Simpler DAX formulas — filter context flows naturally from dimensions to facts
• Faster query performance (VertiPaq engine optimized for star schemas)
• Easier to understand and maintain
• Better compression compared to denormalized flat tables
Q4 — Infosys, HCL
What is the difference between DirectQuery, Import, and Live Connection in Power BI?
Model Answer
Import Mode: Data is imported into Power BI's in-memory VertiPaq engine. Fastest performance. Data refreshed on schedule. 1GB model size limit (default).
DirectQuery: No data stored in Power BI. Every visual sends a live query to the source database. Always up-to-date. Slower performance. Complex DAX restrictions apply.
Live Connection: Used for SSAS / Power BI Premium datasets. No local model — queries are sent to an existing tabular model. Used for enterprise-scale deployments.
DirectQuery: No data stored in Power BI. Every visual sends a live query to the source database. Always up-to-date. Slower performance. Complex DAX restrictions apply.
Live Connection: Used for SSAS / Power BI Premium datasets. No local model — queries are sent to an existing tabular model. Used for enterprise-scale deployments.
📘 DAX Interview Questions
Q5 — TCS, Wipro (Most Asked!)
What is the difference between CALCULATE and FILTER in DAX?
Model Answer
CALCULATE modifies the filter context of an expression. It's the most powerful DAX function — it can add, remove, or override filters.
FILTER is an iterator that returns a table of filtered rows from a given table. It does NOT change the filter context; it creates a subset of rows.
Key difference: CALCULATE changes context; FILTER returns a table.
FILTER is an iterator that returns a table of filtered rows from a given table. It does NOT change the filter context; it creates a subset of rows.
Key difference: CALCULATE changes context; FILTER returns a table.
-- CALCULATE example: Total sales for North region only
North Sales = CALCULATE(SUM(Sales[Amount]), Region[Name] = "North")
-- FILTER inside CALCULATE for complex conditions
High Value Sales = CALCULATE(
SUM(Sales[Amount]),
FILTER(Sales, Sales[Amount] > 10000)
)
Q6 — Infosys
Write a DAX measure to calculate Year-to-Date (YTD) sales.
Model Answer
-- Using TOTALYTD (simplest approach)
YTD Sales = TOTALYTD(SUM(Sales[Amount]), Dates[Date])
-- Using DATESYTD (more flexible)
YTD Sales = CALCULATE(
SUM(Sales[Amount]),
DATESYTD(Dates[Date])
)
-- For financial year ending March 31
FY YTD Sales = TOTALYTD(SUM(Sales[Amount]), Dates[Date], "03-31")
Q7 — TCS, Capgemini
What is RELATED() and RELATEDTABLE() in DAX?
Model Answer
RELATED() — Used in a many-side table to look up a value from the one-side table following the relationship. Works row-by-row (row context).
RELATEDTABLE() — Used in the one-side table to return all related rows from the many-side table. Returns a table, used with iterators like COUNTROWS, SUMX.
RELATEDTABLE() — Used in the one-side table to return all related rows from the many-side table. Returns a table, used with iterators like COUNTROWS, SUMX.
-- RELATED: Get product category in Sales table
Category = RELATED(Products[Category])
-- RELATEDTABLE: Count orders per customer
Order Count = COUNTROWS(RELATEDTABLE(Orders))
📕 Data Modelling & Performance Questions
Q8 — Senior Level (5+ Years)
How do you optimize a slow Power BI report?
Model Answer
Performance optimization steps:
1. Use Performance Analyzer — identify which visuals take the most time
2. Reduce DAX complexity — avoid nested iterators, use variables (VAR)
3. Remove unused columns from the model — every column increases memory
4. Use aggregations for large datasets
5. Use Import mode instead of DirectQuery where possible
6. Avoid bidirectional relationships unless necessary
7. Reduce visual interactions — limit cross-filtering between visuals
8. Use Tabular Editor + Best Practice Analyzer to find model issues
1. Use Performance Analyzer — identify which visuals take the most time
2. Reduce DAX complexity — avoid nested iterators, use variables (VAR)
3. Remove unused columns from the model — every column increases memory
4. Use aggregations for large datasets
5. Use Import mode instead of DirectQuery where possible
6. Avoid bidirectional relationships unless necessary
7. Reduce visual interactions — limit cross-filtering between visuals
8. Use Tabular Editor + Best Practice Analyzer to find model issues
Q9 — Wipro, Infosys
What is Row Level Security (RLS) in Power BI?
Model Answer
RLS is a security feature that restricts data access for report viewers based on their identity (email or role). Users only see data they are authorized to see — even though they're viewing the same report.
There are two types:
• Static RLS: Filter is hardcoded in the role definition
• Dynamic RLS: Filter uses
There are two types:
• Static RLS: Filter is hardcoded in the role definition
• Dynamic RLS: Filter uses
USERPRINCIPALNAME() to auto-filter based on logged-in user's email
-- Dynamic RLS DAX filter
[Email] = USERPRINCIPALNAME()
Q10 — TCS, HCL
What is the difference between Power BI Desktop, Power BI Service, and Power BI Mobile?
Model Answer
Power BI Desktop: Free Windows app for building reports and data models. Used by developers and data analysts.
Power BI Service (app.powerbi.com): Cloud-based platform for publishing, sharing, and collaborating on reports. Includes dashboards, dataflows, and scheduled refresh.
Power BI Mobile: iOS/Android app for viewing and interacting with published reports on the go. Supports push notifications and offline viewing.
Power BI Service (app.powerbi.com): Cloud-based platform for publishing, sharing, and collaborating on reports. Includes dashboards, dataflows, and scheduled refresh.
Power BI Mobile: iOS/Android app for viewing and interacting with published reports on the go. Supports push notifications and offline viewing.
✅ Power BI Interview Tips for TCS/Infosys
- Always mention a real project where you used Power BI — interviewers love examples
- Know the difference between Measure vs Calculated Column — asked in 90% of interviews
- Be clear on Star Schema vs Snowflake Schema — modelling questions are common
- Practice writing basic DAX measures from scratch — YTD, MoM, RANKX
- Know at least 2-3 ways to improve report performance
- Understand RLS — it's asked in almost every senior-level interview
📊
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