20+ Power BI Developer Interview Questions and Answers for Freshers

Performance of reports can be improved by optimizing queries, reducing data volume, using efficient visuals, and caching data.

• Optimize queries by removing unnecessary columns and filters

• Reduce data volume by aggregating data at the source or using incremental refresh

• Use efficient visuals like matrix instead of tables for large datasets

• Cache data to reduce query times for frequently accessed data

Data modeling is the process of creating a visual representation of data to analyze and make informed decisions. DAX is a formula language in Power BI used for calculations.

• Data modeling involves organizing and structuring data to create relationships between different data sets.

• DAX (Data Analysis Expressions) is a formula language used in Power BI to perform calculations and create custom measures.

• Calculating revenue using DAX involves summing up the product of price and qua...read more

Measures are dynamic calculations based on the data model, while calculated columns are static calculations added to a table.

• Measures are used in visualizations and change based on filters and slicers

• Calculated columns are added to a table and are not affected by filters or slicers

• Creating a custom table involves defining the columns and their data types, and then populating it with data

• Custom tables can be created using Power Query or DAX formulas

CALCULATED function is used in Power BI to create custom calculations based on existing data in a report.

• CALCULATED function is used to create custom calculations in DAX (Data Analysis Expressions) language.

• It allows users to define complex calculations based on existing data in the report.

• CALCULATED function can be used with other DAX functions to perform calculations like aggregations, comparisons, and conditional logic.

• Example: CALCULATED column can be used to calculate pr...read more

I have used complex DAX functions like CALCULATE, FILTER, SUMX, etc. to perform advanced calculations in Power BI.

• Used CALCULATE function to apply filters and context changes to calculations

• Utilized FILTER function to filter data based on specific conditions

• Implemented SUMX function to iterate over a table and perform calculations for each row

Calculated column is a static column in a table calculated based on a formula, while Measure is a dynamic calculation based on aggregated data.

• Calculated column is created in Power BI using DAX formula and stored in the data model.

• Measure is a calculation performed on the fly based on the context of the visualization.

• Calculated columns are static and can be used for filtering and sorting, while Measures are dynamic and used for aggregations like sum, average, etc.

Data query is the process of retrieving specific data from a database, while data flow is the movement of data from one point to another.

• Data query involves writing SQL queries to extract specific data from a database

• Data flow refers to the movement of data from source to destination through various transformations

• Data query is used to filter and retrieve relevant data, while data flow ensures data is processed and moved efficiently

• Example: Data query can be used to extract s...read more

Query folding in Power BI is a process where Power BI pushes the data transformation steps back to the data source.

• Query folding improves performance by reducing the amount of data loaded into Power BI.

• It allows Power BI to leverage the capabilities of the data source for data transformation.

• Commonly used with relational databases like SQL Server, Oracle, etc.

• Example: When filtering data in Power BI, query folding will push the filter operation back to the database for proces...read more

RANK assigns a unique rank to each row based on a specified column, while DENSE RANK assigns a unique rank to each distinct row.

• RANK function is used to assign a unique rank to each row based on a specified column

• DENSE RANK function is used to assign a unique rank to each distinct row, skipping ranks if there are ties

• RANK and DENSE RANK are commonly used in SQL queries to rank data based on certain criteria

I would like to assess the candidate's knowledge of Power BI tools, DAX formulas, data modeling, and visualization techniques.

• Power BI tools such as Power Query, Power Pivot, and Power View

• DAX formulas for creating calculated columns and measures

• Data modeling techniques for creating relationships between tables

• Visualization techniques for creating interactive reports and dashboards

Power Query is used to import and transform data within Power BI, while Direct Query allows real-time data access from the data source.

• Power Query is used to import and transform data within Power BI before loading it into the data model.

• Direct Query allows Power BI to query the data source directly in real-time, without importing the data into the data model.

• Power Query is suitable for smaller datasets that can be loaded into memory, while Direct Query is ideal for large dat...read more

Power BI components include Power Query, Power Pivot, Power View, Power Map, and Power Q&A.

• Power Query: Used for data extraction and transformation.

• Power Pivot: Used for data modeling and analysis.

• Power View: Used for interactive data visualization.

• Power Map: Used for geographical data visualization.

• Power Q&A: Allows users to ask questions in natural language and get answers from data.

Types of context refer to the different ways in which data can be analyzed and interpreted in Power BI.

• Row context: evaluates calculations row by row

• Filter context: applies filters to data before calculations

• Query context: used in DAX queries to retrieve data

• Relationship context: determines how tables are related

Power BI software is used for data visualization and analysis.

• Allows for easy creation of interactive reports and dashboards

• Provides real-time data insights

• Integrates with various data sources

• Enables collaboration and sharing of reports

• Helps in making data-driven decisions

INNER JOIN is used to combine rows from two or more tables based on a related column between them.

• Use INNER JOIN to retrieve rows from both tables that have matching values in the specified column

• Syntax: SELECT column_name(s) FROM table1 INNER JOIN table2 ON table1.column_name = table2.column_name

• Example: SELECT Orders.OrderID, Customers.CustomerName FROM Orders INNER JOIN Customers ON Orders.CustomerID = Customers.CustomerID

M language is a powerful data transformation language used in Power Query in Power BI.

• M language is used to transform and clean data in Power BI.

• It is a functional language with a wide range of functions and operators.

• M language is case-sensitive and uses a step-by-step approach to data transformation.

• Examples of M language functions include Table.TransformColumns and List.Transform.

Power BI offers different data connection modes including Import, DirectQuery, and Live Connection.

• Import mode: Data is imported into Power BI and stored in a local model.

• DirectQuery mode: Queries are sent directly to the data source in real-time.

• Live Connection mode: Power BI connects directly to the data source without importing data.

• Each mode has its own advantages and limitations based on data size, refresh frequency, and data source capabilities.

Calculated columns are static values calculated at the row level, while measures are dynamic values calculated at the aggregate level.

• Calculated columns are stored in the data model and can be used in visuals directly.

• Measures are calculated on the fly based on the context of the visualization or report.

• Calculated columns are useful for creating new columns based on existing data, while measures are used for aggregations like sum, average, etc.

Power BI is a business analytics service by Microsoft that provides interactive visualizations and business intelligence capabilities.

• Powerful data visualization tool

• Allows users to create interactive reports and dashboards

• Integrates with various data sources

• Provides business intelligence capabilities

• Can be used for data modeling and analysis

• Offers a wide range of customization options

• Can be accessed through web and mobile devices

Power BI is a business analytics tool by Microsoft that provides interactive visualizations and business intelligence capabilities.

• Power BI is a business analytics tool by Microsoft

• It allows users to create interactive visualizations and reports

• Users can connect to various data sources to import data

• Power BI offers a wide range of data visualization options such as charts, graphs, and maps

• Users can share and collaborate on reports with others

Gateway setup and configuration involves connecting on-premises data sources to Power BI Service.

• Install and configure the On-premises data gateway on a server within the network

• Register the gateway in the Power BI Service

• Create data source connections in Power BI Service using the gateway

• Ensure proper network and firewall configurations for communication between Power BI Service and on-premises data sources

Power BI has two modes: Import mode and DirectQuery mode.

• Import mode: Data is imported into Power BI and stored in a local cache for faster performance.

• DirectQuery mode: Data stays in the original data source and queries are sent directly to the source for real-time data.

• Import mode is suitable for smaller datasets while DirectQuery mode is better for larger datasets or when real-time data is needed.

DAX stands for Data Analysis Expressions and is a formula language used in Power BI for creating custom calculations.

• DAX is used to create custom calculations in Power BI, similar to Excel formulas.

• It can be used to create calculated columns, measures, and calculated tables.

• DAX functions can be used to manipulate data, perform calculations, and create complex expressions.

• Examples of DAX functions include SUM, AVERAGE, CALCULATE, and RELATED.