Power BI Interview Questions and Answers

This section covers frequently asked Power BI interview questions, suitable for both entry-level and experienced candidates. The questions cover various aspects of Power BI, from its core functionality to comparisons with other BI tools.

What is Business Intelligence (BI)?

Business intelligence (BI) uses technology to analyze and visualize business data, providing insights to support better decision-making. BI tools help organizations understand trends, patterns, and key performance indicators (KPIs).

What is Power BI?

Power BI is Microsoft's business analytics service. It's a collection of software services, apps, and connectors that work together to turn your data into visually compelling insights. It is a self-service business intelligence (SSBI) tool.

Power BI Desktop

Power BI Desktop is a free application for creating and managing Power BI reports and dashboards. It connects to data sources, allows data transformation and modeling, and creates interactive visualizations. You can publish your work to the Power BI service for sharing.

Self-Service Business Intelligence (SSBI)

SSBI empowers business users to perform data analysis and create reports and visualizations without needing extensive technical expertise. This democratizes data access and speeds up insight generation.

Components of Microsoft's SSBI Solution

• Power BI Desktop: The desktop application for report creation.
• Power BI service: The online service for sharing and collaborating on reports.

Reasons for Power BI's Popularity

• Pre-built content for SaaS applications.
• Secure data connections (cloud and on-premises).
• Fast deployment and flexible configuration.
• Real-time dashboards.
• Natural language query capabilities.

Power BI Components

Power BI consists of several components:

• Power BI Desktop
• Power BI service
• Power BI mobile apps
• Power BI Report Server
• Power BI Gateway
• Power BI Embedded
• Power Pivot
• Power Query
• Power Map
• Power View
• Data Management Gateway
• Data Catalog
• Power BI Q&A

These components can be grouped into data integration, processing, and presentation.

DAX (Data Analysis Expressions) in Power BI

DAX is a formula language used in Power BI to create calculations and measures within data models.

Data Types in DAX

• Numeric
• Boolean
• DateTime
• String
• Decimal

Applications of Power BI

Power BI is used by a wide range of professionals:

• Business analysts
• Data analysts
• Project managers
• Developers
• Database administrators
• IT professionals
• Data scientists

Ease of Use for Beginners

Power BI is designed to be user-friendly, even for those without programming experience. Its intuitive interface and drag-and-drop features make it accessible to a broad audience.

Importance of Power BI

Power BI enables organizations to gain valuable business insights from data. Its dashboards and reports provide effective ways to communicate those insights.

Power BI Pricing

Power BI Desktop is free. Power BI Pro is a subscription service.

Power BI vs. Tableau

Power BI vs. Excel

Power BI offers enhanced data visualization, dashboard sharing, and collaboration features compared to Excel. Excel is often better suited for detailed, cell-level analysis.

Exporting from Power BI to Excel

Export data from Power BI visualizations to a CSV file (which can then be opened in Excel) by selecting the ellipses (three dots) in the top-right corner of any visual and choosing "Export data".

Power BI vs. Tableau (Detailed Comparison)

Business Intelligence as a Career

Business intelligence is a growing field with high demand for skilled professionals. The need for data analysts and BI specialists is expected to continue increasing.

Power BI Learning Curve

Power BI is relatively easy to learn, especially for users already familiar with Excel. It's designed to be user-friendly and doesn't require advanced programming skills.

Power BI Pricing Tiers

Power BI Desktop is free. Power BI Pro (subscription) offers additional features.

Power BI vs. Power BI Pro

Power BI Desktop is for creating reports. Power BI Pro adds features like sharing, collaboration, and scheduled data refreshes.

Power BI Desktop

Power BI Desktop is a free application that allows you to connect to data sources, create reports and dashboards, and publish them to the Power BI service.

Power BI Formats

Power BI is available as a desktop application (Power BI Desktop), a cloud service (Power BI service), and mobile apps.

Power BI Mobile App Support

Power BI offers mobile apps for iOS, Android, and Windows 10 devices, providing convenient access to your dashboards and reports.

• Google Play Store
• Apple App Store
• Microsoft Store

Building Blocks of Power BI

Power BI's core components are:

• Visualizations: Charts, graphs, tables, and other visual representations of data.
• Datasets: The underlying data models.
• Reports: Collections of visualizations based on a dataset.
• Dashboards: A single view summarizing key insights using tiles.
• Tiles: Individual visualizations displayed on a dashboard.

Visualizations in Power BI

Visualizations transform data into easily understandable charts and graphs. Power BI offers a wide range of visualization types for effective data communication.

Power BI Reports

Reports in Power BI are visual presentations of data from a single dataset. They can consist of multiple pages and different visualization types.

Data Sources Compatible with Power BI

Power BI supports various data sources for DirectQuery (real-time connections):

• Azure SQL Database
• Azure SQL Data Warehouse
• Azure Data Explorer
• Google BigQuery
• Amazon Redshift
• And many more...

Power BI System Requirements

To use the free Power BI service, you need a web browser and an email account. For the desktop application (Power BI Desktop), you'll need a compatible operating system. Mobile apps are available for various platforms.

SUM() vs. SUMX() in DAX

Both functions calculate sums. SUM() aggregates a column. SUMX() iterates over a table, applying a calculation to each row before summing the results (allowing for filtering and more complex calculations).

CORR() Function in DAX

The CORR() function calculates the Pearson correlation coefficient between two columns, measuring the linear relationship between them. The result ranges from -1 (perfect negative correlation) to +1 (perfect positive correlation).

Power View

Power View creates interactive data visualizations (charts, maps, etc.) in Excel, Power BI, SharePoint, and SQL Server.

Advantages of Power BI

• Easy integration with other applications.
• Customizable and interactive dashboards.
• Secure report publishing.
• Fast data access.

Disadvantages of Power BI

• Doesn't seamlessly combine data from live connections with imported datasets.
• 1GB data source limit for some import methods.
• Limited parameter passing in dashboards.
• Dashboard and report sharing restrictions (often limited to the same organizational domain).

M Language in Power Query

Power Query uses the M language (a functional language) for data transformation and manipulation.

Responsive Slicers

Responsive slicers in Power BI adjust their size and layout to fit the available space on a report page, improving the report’s appearance and making it easier to read on different devices.

Creating Maps in Power Map

Power Map requires location data (city, state, country, latitude/longitude) to create geographic visualizations.

Power BI Dashboard Features

• Navigation (pages, bookmarks).
• Tiles (visualizations, web content, images).
• Mobile view layout.

Analyzing Power BI Reports in Excel

1. Enable the "Analyze in Excel" feature in the Power BI admin portal.
2. In Power BI, select the dataset.
3. Click the ellipses and choose "Analyze in Excel".
4. Download the data and open in Excel.

Data Source Filters in Power BI

Data source filters apply filtering before data is loaded into the Power BI model. This can improve query performance.

Older vs. Newer Power BI

The newer version of Power BI uses Power BI Desktop (including Power Query, Power Pivot, and Power View), which replaced the older Excel add-in model.

On-premises Gateway

The on-premises data gateway connects Power BI to on-premises data sources (data that isn't in the cloud).

Data Alerts in Power BI

Data alerts are triggered when data values reach specified thresholds. Alerts only function for data that is refreshed.

The Split Function in Power BI

The Split function splits a text string into an array of substrings based on a delimiter.

Power BI Personal Gateway vs. Data Management Gateway

Power BI Designer

Power BI Desktop is now the primary tool for creating reports; it combines capabilities previously found in Power Query, Power Pivot, and Power View.

KPIs (Key Performance Indicators)

KPIs are metrics used to track progress towards specific goals.

DISTINCT() vs. VALUES() in DAX

Both return unique values. VALUES() excludes NULLs; DISTINCT() includes them.

Advantages of DirectQuery

DirectQuery connects directly to data sources, avoiding the 1 GB import limit. However, it typically affects the query speed compared to loading data into the model directly.

Incremental Refresh

Incremental refresh in Power BI only refreshes changed data, improving performance.

Filters vs. Slicers

Filters: Restrict data visibility in a report or dashboard; users cannot change them. Slicers: Allow users to filter data interactively.

Report Development Window Tabs

• Report
• Data
• Modeling

Default Visualizations in Power BI

Power BI offers a wide variety of visualization types.

New Columns vs. New Measures in Power BI

A new column adds data to the data model. A new measure defines a calculation performed on the fly.

Join Types in Power BI

• Horizontal (Append): Adds data from multiple tables.
• Vertical (Merge): Combines related data from different tables.

Dynamically Changing Measures

[Explain how to dynamically switch between multiple measures in a visual using techniques like a slicer and the SWITCH function.]

Business Email Requirement

Power BI often requires a business email address for account creation.

The SWITCH Function in DAX

[Explain how the SWITCH function allows you to select and perform an operation based on different values.]

The startsWith() Function in DAX

The STARTSWITH() function in Data Analysis Expressions (DAX) checks if one string begins with another string. It returns TRUE if the first string starts with the second, and FALSE otherwise. This function is case-sensitive.

Embed Code in Power BI

The Embed code is a feature in Power BI that provides a link (URL) or an iframe code snippet that you can use to embed reports into other applications or websites.

Time Intelligence Functions in Power BI

Time intelligence functions in Power BI are used to perform calculations and comparisons on time-series data. This includes functions for calculating moving averages, year-over-year growth, and other time-based aggregations. These functions are powerful for analyzing trends and patterns in temporal data.

Hiding and Unhiding Reports in Power BI

1. Open the report in Power BI.
2. Go to the "View" tab.
3. Select the "Selection Pane".
4. Click the eye icon to hide or unhide a report element.