What are the most asked Power BI interview questions?

The difference between calculated columns and measures, star schema design, how CALCULATE works, filter context versus row context, and how you would fix a slow or incorrect report.

Is DAX difficult to learn?

The syntax is straightforward. The difficulty is filter context, which is conceptual rather than syntactic. Most people find it clicks only after building several models and debugging measures that return unexpected numbers.

Do I need Power BI certification to get a job?

It helps at the resume screening stage but rarely decides the outcome. Interviewers weight a dashboard you can explain in depth far more heavily than a certification badge.

Power BI or Tableau for the Indian job market?

Power BI appears in more Indian job listings, largely because of Microsoft ecosystem adoption. The modelling and storytelling skills transfer between them in a week or two.

Power BI Interview Questions and Answers

What these interviews really test

Candidates prepare by learning to build visuals, then get asked about relationships and filter context. Anyone can place a chart on a canvas. Far fewer can build a model that stays correct when a user filters it in an unexpected way, and that is precisely what an interviewer probes.

Data modelling

What is a star schema and why is it preferred in Power BI?

A central fact table containing measurable events, surrounded by dimension tables containing descriptive attributes. Power BI's engine is optimised for this shape, so star schemas give faster, simpler and more predictable models than heavily normalised or flattened alternatives.

What is the difference between a fact table and a dimension table?

A fact table stores events and numeric measures, such as sales transactions, and is typically long. A dimension table stores descriptive context such as product, customer or date, and is typically shorter and wider.

Explain one-to-many and many-to-many relationships.

One-to-many is the normal and desirable case: one row in a dimension relates to many rows in a fact table. Many-to-many relationships are supported but introduce ambiguity in filter direction and are usually a signal that the model needs a bridge table.

What is a bridge table and when do you need one?

An intermediate table that resolves a many-to-many relationship into two one-to-many relationships. You need one when two tables legitimately relate many-to-many, such as students and courses.

Why is a dedicated date table recommended?

Time intelligence functions in DAX require a continuous date table marked as a date table. Relying on dates scattered in fact tables produces wrong or inconsistent results for anything year-to-date or year-on-year.

DAX, the part that decides the interview

What is the difference between a calculated column and a measure?

A calculated column is computed row by row and stored in the model, consuming memory and evaluated at refresh. A measure is computed at query time based on the current filter context and consumes almost no storage. The rule of thumb is to use measures for aggregations and calculated columns only when you need a value to slice or filter by.

Explain filter context and row context.

Row context is the current row during iteration, which is what a calculated column or an iterator function like SUMX operates in. Filter context is the set of filters applied by slicers, rows, columns and visuals when a measure is evaluated. Most DAX confusion comes from not knowing which context is active.

What does CALCULATE do?

CALCULATE evaluates an expression under a modified filter context. It is the most important function in DAX, and it is also where most mistakes happen, because it can both add and override filters.

What is the difference between SUM and SUMX?

SUM aggregates a single column directly. SUMX iterates row by row, evaluates an expression for each row, then sums the results. Use SUMX when the calculation must happen per row before aggregation, such as quantity multiplied by unit price.

What do ALL and REMOVEFILTERS do?

Both remove filters from the specified table or columns, which is how you calculate a percentage of total: divide the current value by the same measure evaluated with ALL applied.

How would you calculate year-on-year growth?

Create a measure for the current period, a second measure using SAMEPERIODLASTYEAR or DATEADD inside CALCULATE, then divide the difference by the prior value. This requires a properly marked date table.

Power Query and data preparation

What is the difference between Power Query and DAX?

Power Query, using M, shapes and cleans data before it enters the model, at refresh time. DAX calculates on data already in the model, at query time. The general guidance is to do transformations as far upstream as possible.

What is query folding and why does it matter?

Query folding is Power Query pushing transformation steps back to the source database as SQL rather than processing them locally. It dramatically improves refresh performance, and certain steps break folding, so the order of steps matters.

What is the difference between Import and DirectQuery?

Import loads data into the model, giving fast performance but data only as fresh as the last refresh. DirectQuery leaves data at the source and queries it live, giving current data but slower interaction and DAX limitations. Choose based on data volume and how fresh the data genuinely needs to be.

Scenario questions

A stakeholder says your dashboard numbers are wrong. What do you do?

Reproduce their exact filter selections first, because most reported discrepancies come from comparing different filter contexts. Then trace back through the measure, the model relationships and the source data. Ask what number they expected and where it came from, because the other source is sometimes the one that is wrong.

Your report is slow. How do you fix it?

Reduce the data first: remove unused columns, filter rows at source and prefer a star schema. Then check for expensive calculated columns that should be measures, bidirectional relationships, and visuals with very high cardinality. Use Performance Analyzer to find which visual actually costs the time rather than guessing.

How do you decide which chart to use?

Match the chart to the question. Comparison across categories suits bars, change over time suits lines, and composition can suit stacked bars though rarely pie charts. The strongest answer usually mentions that the dashboard should answer a specific business question rather than display everything available.

The portfolio question

Almost every Power BI interview includes some version of "walk me through a dashboard you built". Prepare one properly: what business question it answered, how you modelled the data, which measures were non-trivial, what you would change now, and what decision it actually influenced. The last point is the one most candidates cannot answer, and it is the one that distinguishes them.

Power BI is covered in depth in the Power BI course, the AI-Powered Data Analytics certification and the Post Graduate Program, each of which ends in a dashboard you present to a panel.

Power BI Interview Questions and Answers for Analysts