📊 Data Analyst Interview Series — Part 11

Guys, let's continue our Data Analyst Interview Series.

We have covered SQL and Excel. Now let's start one of the most important tools for Data Analysts — Power BI. 📊

Here are 10 important Power BI interview questions to start with. 👇

1️⃣ What is Power BI?

Sample Answer:

“Power BI is a business intelligence and data visualization platform from Microsoft. It allows users to connect to different data sources, transform and model data, create interactive reports and dashboards, and share insights with business users.

As a Data Analyst, I can use Power BI to turn raw data into interactive reports that help stakeholders understand performance and make decisions.”

2️⃣ What are the main components of Power BI?

Sample Answer:

“The major components I commonly work with are:

• Power BI Desktop — used to connect, transform, model, and visualize data.

• Power BI Service — used to publish, share, collaborate, and manage reports and dashboards.

• Power Query — used for data extraction and transformation.

• DAX — used to create measures, calculated columns, and calculated tables.

• Data Model — defines relationships between tables and enables analysis.

• Power BI Mobile — allows users to access reports on mobile devices.”

3️⃣ What is Power Query in Power BI?

Sample Answer:

“Power Query is the data transformation and preparation engine in Power BI.

I use it to connect to different data sources and perform transformations such as removing duplicates, handling missing values, changing data types, filtering rows, splitting columns, merging tables, and appending datasets.

One major advantage is that the transformation steps are saved and can be reapplied automatically whenever the data is refreshed.”

4️⃣ What is DAX?

Sample Answer:

“DAX stands for Data Analysis Expressions. It is the formula language used in Power BI for creating calculations in the data model.

DAX is commonly used to create measures, calculated columns, and calculated tables.

For example, a simple measure for total sales could be:

Total Sales = SUM(Sales[Sales Amount])

DAX becomes particularly powerful when calculations need to respond dynamically to filters and the report's filter context.”

5️⃣ What is the difference between a measure and a calculated column?

Sample Answer:

“A calculated column is calculated row by row and stored in the model.

A measure is calculated when it is used in a visual and responds to the current filter context.

For example, if I need a row-level calculation such as:

Profit = Sales[Revenue] - Sales[Cost]

a calculated column might be appropriate.

But for a KPI such as total profit:

Total Profit = SUM(Sales[Profit])

I would generally use a measure.”

6️⃣ What is a relationship in Power BI?

Sample Answer:

“A relationship connects tables using related columns.

For example, a Sales table may contain Product_ID and a Product table may also contain Product_ID. The relationship allows fields from the Product table to filter and analyze the Sales table.

Creating relationships correctly is critical because incorrect relationships can produce incorrect report results.”

7️⃣ What is the difference between a fact table and a dimension table?

Sample Answer:

“A fact table generally contains transactional or measurable business events, such as sales, orders, or transactions.

A dimension table contains descriptive information used to analyze those events, such as Customer, Product, Region, or Date.

For example:

Fact table → Sales

Dimension tables → Customer, Product, Date, Region

This structure makes the data model easier to analyze and maintain.”

8️⃣ What is a star schema?

Sample Answer:

“A star schema is a data modeling approach where a central fact table is connected to multiple dimension tables.

For example: