Choosing when to use DirectQuery for Power BI datasets is a fundamental decision when designing and implementing enterprise-scale analytics solutions using Microsoft Azure and Microsoft Power BI. For those unfamiliar, Power BI is a tool set that allows business analytics to provide interactive visualizations and business intelligence capabilities. In Power BI, you can connect to data in a couple of different ways – through Import or DirectQuery mode.
In Import mode, the data is imported into the Power BI report, and all processing is performed in the Power BI server. On the other hand, DirectQuery mode involves leaving the data at the source and running queries against the data source when a user interacts with a visualization.
Factors influencing the decision to use DirectQuery mode
Now, let’s explore the factors that might influence your decision to use DirectQuery mode:
- Data Volume: If your dataset is very large, it might not even be possible to import it into Power BI, making DirectQuery a more suitable option. Furthermore, with DirectQuery, you can leverage the full power of the underlying database, which might be a high-performance database server that can handle much larger volumes than Power BI’s import mode.
- Real-time Reporting Requirements: If your use case requires accessing real-time data or very frequent updates, DirectQuery is a good choice. This is because, in Import mode, the data refreshes on a schedule and therefore might not reflect the latest updates.
- Security: DirectQuery mode may be the preferred option if you have row level security setup at the data source and want to leverage it in your Power BI reports.
- Compliance Requirements: Some organizations have compliance requirements that prevent data from being copied from its original location. In these cases, DirectQuery can be the only feasible choice because the data remains at the source.
Limitations of DirectQuery
However, using DirectQuery also comes with certain limitations that you should be aware of:
- Performance can be slower than import mode since each interaction with a visualization makes a round trip to the underlying source to retrieve the data.
- There are limitations to DAX formulas and certain Power BI features may not work as expected.
- The underlying source must be available and properly configured to support DirectQuery connections.
- There are limitations with blending data from other sources when using DirectQuery mode.
It’s worth noting that, for scenarios where you want to maintain the advantages of DirectQuery but also mitigate some of its limitations, you can use Power BI’s Composite Model feature. This allows you to mix Import and DirectQuery in the same report.
In Conclusion
In conclusion, whether to use DirectQuery for Power BI datasets is not a one-size-fits-all decision. It depends on your specific requirements and constraints. In the DP-500 exam, you may encounter questions related to this topic, so it’s crucial to understand when and why you should use DirectQuery over Import mode in Power BI.
Practice Test
True or False: DirectQuery is a connection type that can be used when you want to always reflect the current state of the data source in your Power BI reports?
Answer: True.
Explanation: True, DirectQuery is used when your reports always need to reflect the current state of the data source, not a cached copy of the data source.
Which of the following is NOT a scenario when you would use DirectQuery for your Power BI datasets?
- a) Your dataset is larger than 1GB
- b) You want to minimize the amount of data transferred
- c) You have regulatory requirements to not copy data
- d) Your data is static and doesn’t change frequently
Answer: d) Your data is static and doesn’t change frequently.
Explanation: DirectQuery is ideal for situations where data is changing frequently, and you need up-to-date data reflected in your Power BI reports.
True or False: DirectQuery in Power BI allows users to execute direct queries against the underlying data in the data source.
Answer: True
Explanation: DirectQuery does execute direct queries against the underlying data in the data source, ensuring that the data is always up-to-date.
All Power BI connectors support DirectQuery. True or False?
Answer: False.
Explanation: Not all Power BI connectors support DirectQuery. Some connectors do not, such as SharePoint Lists or Blob storage.
Which selection below is NOT a benefit of using DirectQuery with Power BI?
- a) Always up-to-date data
- b) Reducing the size of the data model
- c) Offloading processing to the source system
- d) High performance for large datasets
Answer: d) High performance for large datasets
Explanation: DirectQuery may not always provide high performance for large datasets as each interaction with the report queries the underlying data source directly, which can result in slower performance.
True or False: Using DirectQuery instantly improves the performance of your Power BI reports.
Answer: False.
Explanation: DirectQuery can actually slow down performance as each query runs directly on the data source.
DirectQuery mode supports all data transformations in Power BI. True or False?
Answer: False.
Explanation: Some data transformations in Power Query are not supported when you’re using DirectQuery mode.
True or False: With DirectQuery, you can explore data that’s beyond the limit imposed by the Power BI service.
Answer: True.
Explanation: DirectQuery allows you to bypass the data volume restrictions of Power BI due to its direct interaction with the source data.
Which of these scenarios suit the use of DirectQuery?
- a) Need for real-time data
- b) Restrictions on data movement
- c) Large volume datasets
- d) Data source supports SQL.
Answer: all (a, b, c, and d)
Explanation: All of these scenarios aptly fit the use of DirectQuery in Power BI due to its real-time interaction with the data source.
The use of DirectQuery is recommended when model refresh times are long due to the size or complexity of the data source. True or False?
Answer: False.
Explanation: DirectQuery can make interactions slower when dealing with large or complex data sources due to the live querying process. Therefore, it’s not recommended in such situations.
Interview Questions
What is DirectQuery in Power BI?
DirectQuery is a data connection method in Power BI that offers a live and direct connection to a data source. With DirectQuery, data remains in the original source and Power BI sends query commands to the source when creating visuals, instead of importing or loading data into Power BI.
When should you use DirectQuery in Power BI datasets?
You should use DirectQuery when your dataset is too large to be imported into Power BI, near-real-time updates are needed, data is required to remain on-premise, or if the underlying data changes frequently requiring up-to-the-minute reports.
What is the major limitation of using DirectQuery in Power BI?
The major limitation of using DirectQuery is that it doesn’t support all Power BI’s data modeling features and DAX functions that are available when you import data.
Does Power BI support DirectQuery over multiple databases?
Yes, Power BI can use DirectQuery over multiple databases enabling single report from multiple DirectQuery sources or a mix of DirectQuery and import data.
Can we use DirectQuery for all data sources in Power BI?
No, DirectQuery is not supported by all data sources. A list of supported data sources is provided within Power BI documentation.
Do data privacy settings impact DirectQuery?
Yes, data privacy levels set for different sources can restrict the execution of a DirectQuery, based on the combination of sources involved in the query.
How does Power BI performance relate to the performance of the underlying data source in DirectQuery mode?
The performance of Power BI reports in DirectQuery mode relies heavily on the performance of the underlying data source. If the source performs slowly, the reports will also be slow.
Can we create a calculated column while using DirectQuery for Power BI datasets?
Yes, you can create calculated columns while using DirectQuery, but the calculations are performed during report loading, which can affect performance.
What is Composite Model in the context of DirectQuery?
Composite Model is a feature in Power BI that allows one to use DirectQuery and imported data in the same report, giving the ability to combine data from multiple data sources.
Can DirectQuery be used in conjunction with Power BI’s dataflow?
No, DirectQuery is not currently supported in Power BI’s dataflow. Dataflows can only import data for now.
Does using DirectQuery reduce the RAM requirement for Power BI?
Yes, as data is not loaded into memory in Power BI, using DirectQuery has less impact on RAM than importing data.
Do DirectQuery use the same relationship types as import mode in Power BI?
No, DirectQuery can only use “Single” direction for cross-filter direction in relationships, unlike both “Single” and “Both” in import mode.
Can you use Power Query when using DirectQuery in Power BI?
Yes, you can use Power Query, but any transformations you apply will result in SQL queries being generated and run on the source database, which could impact performance.
Can you refresh a DirectQuery dataset in Power BI?
Unlike imported datasets that need to be scheduled for refresh, DirectQuery datasets are always up-to-date and do not need to be refreshed.
Which would be faster, a report based on DirectQuery or import mode in Power BI?
Generally, reports based on import mode would be faster because data is loaded into memory. But this will vary based on the size of the dataset, speed of data source, network latency etc.
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