1. What is Power BI and what are its primary components?
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Power BI is a Microsoft analytics tool designed to visualize data, generate reports, and share insights efficiently. Its main components include Power BI Desktop for report creation, Power BI Service for cloud-based sharing and collaboration, and Power BI Mobile for accessing dashboards on the go. Together, these components provide a seamless data analysis experience across multiple platforms.
2. How can data be imported from different sources into Power BI?
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Data can be imported from Excel, SQL databases, cloud storage, web APIs, and other sources using the Get Data feature in Power BI Desktop. Once connected, the data can either be loaded into the model or accessed directly for live queries. This allows flexibility in handling a wide variety of business datasets efficiently.
3. What is DAX, and how does it differ from Power Query?
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DAX, or Data Analysis Expressions, is a formula language used to perform calculations and aggregations on data already loaded into the Power BI model. Power Query, in contrast, is used to clean, transform, and shape raw data before it is imported. Essentially, Power Query prepares the data, while DAX performs computations within the dataset for analysis.
4. How do calculated columns differ from measures in Power BI?
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Calculated columns are stored in the data model and computed for each row, making them available for visuals and other calculations. Measures, on the other hand, are dynamic calculations evaluated on demand based on filters or visual context. While calculated columns occupy storage, measures offer efficient, on-the-fly aggregations without increasing dataset size.
5. What is row-level security (RLS) and how is it applied in Power BI?
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Row-level security restricts data access so that users only see information relevant to their roles. In Power BI Desktop, roles are defined, and filters are applied to tables to control visibility. Once the report is published to Power BI Service, these roles maintain secure, role-specific access for each user.
6. Which methods can improve the performance of Power BI reports?
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Performance can be enhanced by optimizing complex DAX formulas, removing unnecessary columns, and simplifying the data model. Limiting the number of visuals per page and using aggregated tables also helps. Enabling query folding in Power Query ensures transformations are handled efficiently by the source system.
7. What types of filters can be used in Power BI?
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Power BI offers various filter options to control the data displayed in reports. Visual-level filters affect a single visual, page-level filters influence all visuals on a page, and report-level filters apply to the entire report. Slicers provide interactive filtering, allowing users to dynamically explore and analyze data.
8. Why is a Power BI Gateway necessary?
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A Power BI gateway connects the cloud service with on-premises data securely. It allows scheduled and real-time data refreshes while keeping sensitive information within the company network. This ensures dashboards remain up-to-date while maintaining data security and compliance standards.
9. What methods are used to manage data refresh in Power BI?
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Data refresh ensures reports are updated with the latest information from source systems. In Power BI Service, refreshes can be scheduled automatically, while on-premises data sources require a gateway. Full refreshes reload all data, whereas incremental refreshes update only changed records, improving both efficiency and performance.
10. What distinguishes Import, DirectQuery, and Live Connection modes in Power BI?
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Import mode loads data into Power BI for fast performance but requires scheduled refreshes. DirectQuery connects directly to the data source for real-time access, though queries may be slower. Live Connection links to external Analysis Services models, enabling live interaction with data without importing it into the Power BI model.