L&T Technology Services Power BI Developer Interview Questions and Answers

Q1. WHAT IS ROW LEVEL SECURITY ?
Ans. 
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
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Q2. What is data gateway
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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
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Q3. What is different between filter and slicer?
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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
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Q1. ROW LEVEL SECURITY
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Q2. How to install Data Gateway in power bi
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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
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Q1. Connectivity mode
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Q2. RLS
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Q1. Difference between measure and count
Ans. 
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.
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Q2. What is Row level security
Ans. 
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
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Q3. What are relationships in power BI
Ans. 
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
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Q4. In previous project what type of data source we used
Ans. 
We used a variety of data sources including SQL databases, Excel files, and web APIs.
• SQL databases

• Excel files

• Web APIs
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Q1. What is star schema and snowflake schema?
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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
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Q2. Explain about your experience in SQL joins
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Q3. Tell me what ways you improve performance of report?
Ans. 
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
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Q4. What is data query and data flow?
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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
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Q5. Difference between power query and direct query
Ans. 
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
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Q6. What is RANK & DENSE RANK in SQL
Ans. 
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
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Q7. What is Calculated column and Measure?
Ans. 
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
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Q8. Tell me about complex DAX functions you used
Ans. 
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
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Q9. What is CALCULATED function and how it works?
Ans. 
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
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Q10. What is query folding in power BI?
Ans. 
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
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Q11. Tell me about types of Context
Ans. 
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
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Q12. Fundamentals of POWER BI?
Ans. 
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
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Q13. DDL & DML commands?
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Q14. Give me an example forINNER JOIN in sql
Ans. 
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
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