Power BI Interview Question and Answer

 What is Power BI, and what are its key components?


Answer: Power BI is a business intelligence and data visualization tool by Microsoft. Its key components include Power Query for data transformation, Power Pivot for data modeling, Power View for interactive reporting, and Power Q&A for natural language querying.


What are the different versions of Power BI, and how do they differ?


Answer: Power BI comes in three main versions: Power BI Desktop (for report creation), Power BI Service (for sharing and collaboration), and Power BI Mobile (for mobile access). There is also a Power BI Pro license for sharing reports and a Power BI Premium license for dedicated resources and on-premises use.


Explain the concept of data modeling in Power BI.


Answer: Data modeling in Power BI involves creating relationships between tables, defining calculated columns and measures, and organizing data to build a data model that can be used for interactive reporting and visualization.


How can you import data into Power BI?


Answer: Data can be imported into Power BI from various sources, including databases, Excel files, web services, and online services. Power Query is often used to transform and shape the data during the import process.


What is DAX, and why is it important in Power BI?


Answer: DAX (Data Analysis Expressions) is a formula language used in Power BI to create custom calculations and aggregations for data analysis. It's essential for creating measures and calculated columns.


What are slicers in Power BI, and how do they enhance report interactivity?


Answer: Slicers are visual filters that allow users to filter and interact with the data in reports. They enable dynamic data selection and help users focus on specific aspects of the data.


What is a Power BI gateway, and when is it used?


Answer: A Power BI gateway is used to connect on-premises data sources to the Power BI Service. It ensures that data in on-premises databases can be refreshed and accessed in the cloud-based Power BI Service.


How do you create custom visuals in Power BI?


Answer: Custom visuals in Power BI can be created using Power BI Developer Tools, which includes the Power BI Visuals SDK. Custom visuals allow developers to build and integrate their own visualizations into Power BI reports.


What is the difference between a report and a dashboard in Power BI?


Answer: A report in Power BI is a collection of visualizations and charts, while a dashboard is a single-page, real-time view of data, often created by pinning visuals from one or more reports. Dashboards are used for high-level monitoring.


How can you share Power BI reports with others?


Answer: Power BI reports can be shared through the Power BI Service using various methods, such as sharing a dashboard, publishing to web, exporting as a PDF or PowerPoint, or distributing through Power BI apps.


What is Power Query and how is it used in Power BI?


Answer: Power Query is a data transformation tool in Power BI used to connect, transform, and clean data from various sources. It is essential for data preparation before creating data models and reports.


Explain DirectQuery and Import data connection options in Power BI.


Answer: Import data loads data into the Power BI dataset for faster performance, while DirectQuery connects directly to data sources in real-time. The choice depends on data volume, refresh frequency, and data source capabilities.


How do you optimize the performance of a Power BI report?


Answer: Performance optimization includes reducing unnecessary visuals and columns, using DirectQuery when suitable, applying data modeling best practices, and optimizing DAX calculations to reduce query time.


What are the benefits of using the Power BI REST API?


Answer: The Power BI REST API allows developers to programmatically interact with Power BI, including embedding reports, automating data refresh, and managing datasets. It enhances the extensibility and integration of Power BI.


Can you explain the process of creating a calculated column in Power BI?


Answer: To create a calculated column, you define a DAX expression in the Data Model view. The calculated column's values are calculated for each row in the table based on the DAX expression.


What is the difference between a calculated column and a measure in Power BI?


Answer: A calculated column is a column added to a table that contains a calculated value for each row, whereas a measure is a calculation performed on aggregated data and is typically used in visuals to provide context-specific results.


What is Row-level Security in Power BI, and how is it implemented?


Answer: Row-level security is used to restrict data access for different users or groups. It is implemented by creating roles in Power BI Desktop, defining DAX filters that limit data visibility, and assigning users or groups to these roles in the Power BI Service.


Explain the concept of Power BI DirectQuery Mode and its use cases.


Answer: DirectQuery mode allows Power BI to query data in real-time from a data source without importing it into the Power BI model. It is suitable for scenarios where you need up-to-the-minute data and want to leverage the power of your database system.


What is the Power BI Composite Model, and when would you use it?


Answer: The Composite Model in Power BI allows you to combine DirectQuery and Import data connections within the same model. This is useful when you have data sources with different refresh frequencies or performance requirements.


How can you optimize the performance of a Power BI report when using DirectQuery?


Answer: To optimize DirectQuery performance, consider using query folding, reducing the number of visuals on the page, and using indexed views or materialized views in the underlying data source. Also, make use of query performance tools and performance analyzer in Power BI.


Explain the concept of star schema and snowflake schema in the context of data modeling in Power BI.


Answer: Star schema and snowflake schema are data modeling techniques. In a star schema, you have a central fact table connected to dimension tables. In a snowflake schema, dimension tables may be normalized, creating a more complex schema. Star schemas are often preferred for simplicity and performance in Power BI.


What are the differences between Power BI and Excel for data analysis and visualization?


Answer: Power BI is designed for data analysis, reporting, and data sharing. It excels in handling large datasets, creating interactive reports, and sharing them in the cloud. Excel is a spreadsheet tool that is often used for smaller datasets and individual data analysis.


How do you handle data refresh failures in Power BI, and what are common causes of refresh failures?


Answer: Common causes of data refresh failures include changes in data source credentials, changes in the data schema, or data source connectivity issues. To handle failures, you can set up automated notifications, adjust data source credentials, and monitor data source health.


What is Power BI Embedded, and how is it different from Power BI Service?



Answer: Power BI Embedded allows developers to integrate Power BI reports and dashboards into their own applications, while Power BI Service is a cloud-based platform for creating and sharing reports. Power BI Embedded provides more control and customization for embedding reports into applications.


Explain the concept of Power BI Gateways, and what are the different types of gateways available?


Answer: Power BI Gateways are used to connect on-premises data sources to Power BI Service. There are two types of gateways: the On-premises Data Gateway (used for most scenarios) and the On-premises Data Gateway (Personal Mode), which is used for individual use cases.


What are the benefits and use cases of Power BI Dataflows?


Answer: Power BI Dataflows allow you to create, modify, and enrich data in a Power BI Service workspace. Benefits include data transformation, integration, and data preparation for easy sharing and reuse. Use cases include centralizing data preparation and cleaning tasks.


How can you integrate Power BI with other Microsoft tools and services, such as Azure and SharePoint?


Answer: Integration can be achieved through Power BI connectors and APIs. You can integrate with Azure services like Azure Data Factory, Azure SQL Data Warehouse, and SharePoint for data storage and collaboration.

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