LTIMindtree 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 performa...read more

I have extensive experience using SQL joins to combine data from multiple tables for reporting and analysis in Power BI.

• Inner Join: Combines rows from two tables where there is a match. Example: SELECT * FROM Orders INNER JOIN Customers ON Orders.CustomerID = Customers.CustomerID.

• Left Join: Returns all rows from the left table and matched rows from the right table. Example: SELECT * FROM Customers LEFT JOIN Orders ON C...read more

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 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 mov...read more

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 loa...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

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...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 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 lo...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...read more

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 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 collaborat...read more

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.Cus...read more

Measure is a calculated value based on data in a model, while count is a simple count of records.

• Measure is a calculated value based on aggregation functions like sum, average, etc.

• Count is a simple count of records in a dataset.

• Measures are used in Power BI to perform calculations on data, while count is used to simply count the number of records.

Row level security is a feature in Power BI that restricts data access at the row level based on user roles or criteria.

• Allows users to only see data that is relevant to them

• Can be implemented using DAX expressions

• Helps in maintaining data privacy and security

• Useful for organizations with sensitive data

Relationships in Power BI define how different tables are connected to each other.

• Relationships define how tables are related to each other based on common fields

• They are used to create connections between tables for data analysis

• Relationships can be one-to-one, one-to-many, or many-to-many

• They are essential for creating accurate and meaningful visualizations in Power BI

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

• SQL databases

• Excel files

• Web APIs

Row level security is a feature in Power BI that restricts data access at the row level based on user roles or criteria.

• Row level security limits data access based on user roles or criteria

• It ensures that users only see the data they are authorized to access

• Row level security can be implemented using DAX expressions in Power BI

Data gateway is a tool that connects on-premises data sources with cloud-based applications.

• Data gateway allows for secure transfer of data between on-premises and cloud environments

• It acts as a bridge between on-premises data sources and cloud services like Power BI

• Data gateway helps in maintaining data security and compliance

• Examples of data gateways include Power BI Gateway and Azure Data Gateway

Filters are used to restrict data at the report level, while slicers are interactive visual filters applied to specific visuals.

• Filters are applied at the report level and affect all visuals, while slicers are applied to specific visuals only.

• Slicers allow users to interactively filter data by selecting values from a list or range.

• Filters can be applied to multiple visuals at once, while slicers are applied individuall...read more

Data Gateway can be installed in Power BI by downloading and running the installer.

• Download the Data Gateway installer from the Power BI service

• Run the installer and follow the installation wizard

• Sign in with your Power BI account to register the gateway