200+ Power BI Developer Interview Questions and Answers

Star schema is a data warehouse schema where a central fact table is connected to multiple dimension tables. Snowflake schema is a normalized form of star schema.

• Star schema consists of a central fact table connected to multiple dimension tables

• Snowflake schema is a normalized form of star schema where dimension tables are further normalized into sub-dimension tables

• Star schema is denormalized for faster query performance, while snowflake schema is normalized for easier maint...read more

Reports are detailed and provide specific information, while dashboards are high-level and provide an overview.

• Reports are typically longer and more detailed than dashboards

• Reports are often used to provide specific information to a targeted audience

• Dashboards are high-level and provide an overview of key metrics

• Dashboards are often used to monitor performance and identify trends

• Reports are usually static, while dashboards are interactive and allow for real-time data explorat...read more

Implement security to data using row-level security (RLS)

• Use user roles and permissions to restrict access to specific data

• Leverage Power BI's built-in security features such as dataset security and data categorization

• Implement dynamic security based on user context or attributes

• Utilize Power BI's security features like Azure Active Directory integration for authentication and authorization

Parameters are used for dynamic values that can be changed, while constants are used for fixed values in M query.

• Use parameters for values that may change frequently, such as dates or file paths

• Use constants for values that are fixed, such as column names or static calculations

We used a variety of data sources including SQL databases, Excel files, and web APIs.

• SQL databases

• Excel files

• Web APIs

Distinct vs Null: unique values vs absence of value. Parallel period vs Same period last year: comparing current vs previous time periods.

• Distinct values are unique values in a dataset, while null represents the absence of a value.

• Parallel period compares data from the same time period in different years, while Same period last year compares data from the previous year.

• For example, if we are comparing sales data for January 2021 to January 2020, it would be a parallel period ...read more

Power BI supports three types of relationships: one-to-one, one-to-many, and many-to-many.

• One-to-one: used when two tables have a unique relationship, such as a person and their social security number.

• One-to-many: used when one record in the first table can have multiple matching records in the second table, such as a customer and their orders.

• Many-to-many: used when multiple records in the first table can have multiple matching records in the second table, such as students a...read more

There are three types of filters in Power BI: visual, page, and report level filters.

• Visual filters apply to a single visual or chart.

• Page filters apply to all visuals on a single page.

• Report level filters apply to all visuals and pages in the report.

• Filters can be applied to columns, measures, or hierarchies.

• Examples of filters include date range filters, slicers, and dropdown filters.

Iterators are used to iterate over a table or column, while aggregator functions perform calculations on a set of values.

• Iterators include functions like FILTER, SUMX, and AVERAGEX.

• Aggregator functions include functions like SUM, AVERAGE, and COUNT.

• Iterators are used to perform calculations on a row-by-row basis, while aggregator functions perform calculations on a set of values.

• Iterators can be used to filter data before performing calculations with aggregator functions.

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

SQL is a programming language used to manage and manipulate relational databases. JOIN is used to combine data from multiple tables. Finding the 2nd highest salary involves sorting and selecting the appropriate row.

• SQL is used to manage and manipulate relational databases

• JOIN is used to combine data from multiple tables

• To find the 2nd highest salary, sort the salaries in descending order and select the second row

• Example: SELECT salary FROM employees ORDER BY salary DESC LIMIT...read more

Power BI plays a crucial role in today's market by enabling organizations to visualize and analyze their data for better decision-making.

• Power BI allows businesses to create interactive reports and dashboards for data visualization.

• It helps in analyzing data trends, identifying patterns, and making informed decisions.

• Power BI integrates with various data sources, making it easier to consolidate and analyze data from multiple sources.

• Organizations can use Power BI to track key...read more

Establishing connections with data sources is crucial for Power BI development.

• Identify the data sources you want to connect to, such as databases, files, APIs, etc.

• Use Power BI's built-in connectors to establish connections to various data sources.

• Configure the connection settings, such as server name, database name, authentication method, etc.

• Import or connect to the data from the selected data sources to start building reports and dashboards.

• Refresh the data periodically t...read more

Interaction mode in Power BI allows users to interact with visualizations and explore data in a more dynamic way.

• Interaction mode can be accessed by clicking on the 'Focus mode' button in the top right corner of a visualization.

• In interaction mode, users can hover over data points to see more information, filter data, and drill down into details.

• Users can also use the 'Selection pane' to show or hide specific visualizations or data points.

• Interaction mode is useful for presen...read more

SUM calculates the sum of a column or expression, while SUMX calculates the sum of an expression evaluated for each row in a table.

• SUM is used to calculate the sum of a column or expression in Power BI.

• SUMX is used to calculate the sum of an expression evaluated for each row in a table.

• SUM is typically used with columns, while SUMX is used with tables or filtered tables.

• SUMX can be used to perform more complex calculations by iterating over each row in a table.

I have used DAX time intelligence functions like TOTALYTD, SAMEPERIODLASTYEAR, etc.

• TOTALYTD function calculates the year-to-date total for a given expression

• SAMEPERIODLASTYEAR function returns the value of the same period in the previous year

• DATESYTD function returns a set of dates year-to-date based on the current context

min, minA, minX, max, maxA, maxX are functions in Power BI used to calculate minimum and maximum values.

• min: Returns the smallest value in a column or expression.

• minA: Returns the smallest non-null value in a column or expression.

• minX: Returns the smallest value in a column or expression, considering a specified filter context.

• max: Returns the largest value in a column or expression.

• maxA: Returns the largest non-null value in a column or expression.

• maxX: Returns the largest v...read more

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

Having clause is used with aggregate functions while where clause is used to filter rows

• Having clause is used with GROUP BY to filter groups based on conditions

• Where clause is used to filter rows based on conditions

• Having clause is applied after grouping while where clause is applied before grouping

• Example: SELECT department, AVG(salary) FROM employees GROUP BY department HAVING AVG(salary) > 50000

• Example: SELECT * FROM employees WHERE department = 'IT'

Tableau is more user-friendly and better for data visualization, while Power BI is more powerful for data manipulation and integration.

• Tableau is known for its ease of use and intuitive drag-and-drop interface.

• Power BI has more advanced data manipulation capabilities and better integration with Microsoft products.

• Tableau is better for creating visually appealing dashboards and reports, while Power BI is better for complex data analysis and modeling.

• Power BI offers more advanc...read more

Bulk report migration can be done using Power BI REST API or PowerShell scripts.

• Use Power BI REST API to automate the migration process

• Create PowerShell scripts to handle bulk report migration

• Leverage tools like Power BI Management cmdlets for bulk operations

RLS in Power BI restricts data access based on user roles, ensuring users see only relevant data.

• Define roles in Power BI Desktop using DAX filters to restrict data visibility.

• Example: Create a role 'Sales' with a filter like [Region] = USERNAME() to show data only for the user's region.

• Publish the report to Power BI Service and assign users to the defined roles.

• Test the roles in Power BI Desktop using the 'View as Role' feature to ensure correct data visibility.

A creative dashboard in Power Query involves using unique visuals and interactive elements to present data in an engaging way.

• Utilize custom visuals to display data in a visually appealing manner

• Incorporate interactive elements such as slicers and filters for user-friendly navigation

• Use color coding and formatting to highlight important insights

• Include dynamic elements like tooltips and drill-down capabilities

• Experiment with different chart types and layouts to create a visua...read more

DAX functions are used in Power BI to create custom calculations, manipulate data, and analyze information.

• DAX stands for Data Analysis Expressions

• Common DAX functions include SUM, AVERAGE, MAX, MIN, and CALCULATE

• DAX functions can be used to create calculated columns, measures, and calculated tables

• DAX functions are similar to Excel functions but are optimized for working with relational data models

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

Schema for n Power BI is the structure of the data model used to organize and connect data sources.

• Schema defines the relationships between tables, columns, and measures.

• It helps in creating a logical model of the data.

• Schema can be created using Power BI Desktop or Power BI Service.

• Example: A schema for sales data may include tables for customers, products, and sales transactions.

• Schema can also include calculated columns and hierarchies.

Common data connectivity modes include DirectQuery, Import, Live Connection, and Composite models.

• DirectQuery allows querying data directly from the data source in real-time.

• Import mode imports data into Power BI for faster performance but may not reflect real-time data.

• Live Connection connects Power BI to a data source without importing data.

• Composite models combine DirectQuery and Import modes for flexibility.

Direct query mode connects to data source in real-time, while import mode loads data into Power BI for faster analysis.

• Direct query mode connects to data source in real-time, providing up-to-date data

• Import mode loads data into Power BI for faster analysis, but may not always reflect real-time changes

• Direct query mode is suitable for large datasets that require real-time updates

• Import mode is suitable for smaller datasets or when real-time updates are not necessary

The GROUP BY clause is used in SQL to group rows that have the same values into summary rows.

• It is used with aggregate functions like COUNT, SUM, AVG, etc.

• It helps in summarizing data and generating reports.

• It is often used in conjunction with the HAVING clause to filter grouped data.

• Example: SELECT department, COUNT(employee_id) FROM employees GROUP BY department;

Power BI Developer interview questions related to calculations and date table creation.

• Moving Average can be calculated using DAX functions like AVERAGEX and CALCULATE.

• Rank can be calculated using RANKX function.

• Date Table can be created using CALENDAR function in DAX.

• Previous Month Sales can be calculated using functions like PREVIOUSMONTH and CALCULATE.

You can refresh dimensions using Power BI REST API by sending a POST request to the appropriate endpoint.

• Use the POST method to send a request to the refresh endpoint

• Include the dataset ID and table name in the request body

• Authenticate the request using an access token or API key

I will handle errors on pg by implementing error handling techniques and logging mechanisms.

• Implement try-catch blocks to catch and handle errors

• Use logging frameworks to log errors for troubleshooting

• Display user-friendly error messages to guide users on how to resolve issues

DAX patterns are reusable formulas used to solve common business problems in Power BI.

• DAX patterns are pre-built formulas that can be used to solve common business problems in Power BI

• They are reusable and can be applied to different data models

• Examples of DAX patterns include time intelligence, ranking, and filtering patterns

Row level security in Power BI allows restricting data access based on user roles and filters.

• Row level security can be implemented using roles and filters in Power BI.

• Roles can be created and assigned to users or groups to restrict access to specific data.

• Filters can be applied to tables or columns to limit data visibility based on user roles.

• Row level security can be tested using the View As Roles feature in Power BI Desktop.

• Row level security can also be implemented using ...read more

A published data source is a dataset that has been shared and made accessible to others within an organization.

• Published data sources can be accessed and used by multiple users within an organization.

• They are typically stored in a centralized location for easy access.

• Changes made to a published data source are reflected in all reports that use that data source.

• Examples include shared Excel files, SQL databases, and Power BI datasets.

Extended data sources refer to additional data connections beyond the standard sources in Power BI.

• Extended data sources allow users to connect to a wider range of data sources for analysis.

• Examples of extended data sources include web services, custom APIs, and cloud storage platforms.

• These additional connections enhance the flexibility and capabilities of Power BI for data analysis and visualization.

Time intelligence functions in DAX are used to perform calculations based on dates and times.

• Time intelligence functions help in comparing data over different time periods.

• Functions like TOTALYTD, SAMEPERIODLASTYEAR, and DATESBETWEEN are commonly used for time intelligence.

• They can be used to calculate year-to-date totals, compare values with previous periods, and more.

SSAS cubes can be refreshed using SQL Server Agent jobs, XMLA scripts, or manually through SQL Server Management Studio.

• SSAS cubes can be refreshed using SQL Server Agent jobs scheduled at specific intervals.

• XMLA scripts can be used to automate the process of refreshing SSAS cubes.

• Manual refreshing of SSAS cubes can be done through SQL Server Management Studio by processing the cube.

• Refreshing can also be triggered programmatically using tools like PowerShell scripts.

Power Query Editor allows various transformations on data such as filtering, sorting, merging, splitting, and aggregating.

• Filtering: Removing rows based on certain criteria.

• Sorting: Arranging rows in a specific order.

• Merging: Combining multiple tables or queries into one.

• Splitting: Dividing a column into multiple columns.

• Aggregating: Calculating summary statistics like sum, average, count, etc.

Power BI supports multiple connectivity modes for data sources.

• DirectQuery mode allows real-time data access from the source system.

• Import mode imports data into Power BI for faster performance.

• Live Connection mode connects to an external Analysis Services model.

• Power BI Gateway enables on-premises data access.

• Power BI Dataflows allows data preparation and transformation in the cloud.

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

Calculated columns are columns created in Power BI by using DAX formulas, while measures are calculations based on the data model.

• Calculated columns are static and stored in the data model, while measures are dynamic and calculated on the fly.

• Calculated columns are used for adding new data to a table, while measures are used for aggregating data or performing calculations.

• Examples of calculated columns include adding a new column for profit margin, while measures can be used ...read more

RLS stands for Row-Level Security, a feature in Power BI that restricts data access based on user roles.

• RLS allows you to control which rows of data a user can access in a Power BI report or dashboard

• You can define security roles and rules to filter data based on user attributes or roles

• RLS helps in ensuring data privacy and compliance with regulations

• For example, you can use RLS to restrict a sales manager to only see data related to their region