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Importance of a Solid Data Model: A well-structured data model is the key to unlocking the full potential of Power BI. It determines how data is stored, related, and accessed, directly impacting the performance and usability of your reports.Star Schema vs. Snowflake Schema:
Star Schema:
Characterised by a central fact table surrounded by dimension tables.
Simplifies query performance, enhancing report responsiveness.
Ideal for scenarios where performance is crucial, such as large datasets.
Snowflake Schema:
Normalised structure with hierarchies split into separate tables.
Reduces redundancy and is suitable for complex, normalized data structures.
Offers flexibility but may result in slightly slower query performance compared to the star schema.
DirectQuery vs. Import Data:
DirectQuery:
Connects Power BI directly to the data source for real-time analysis.
Suitable for large datasets where importing would be impractical.
Ensures up-to-the-minute accuracy but may lead to slower visual rendering.
Import Data:
Data is imported into Power BI for faster report generation.
Ideal for smaller to moderately sized datasets.
Ensures high performance but may require periodic refreshes to maintain data accuracy.
Composite Models:
Combining Import and DirectQuery:
Allows a blend of both import and direct query models in a single report.
Suitable for scenarios with a mix of large and small datasets.
Provides flexibility without compromising performance.
Best Practices for Data Modelling in Power BI:
Optimise Relationships:
Establish relationships between tables to facilitate smooth data navigation.
Utilise one-to-many relationships for efficiency.
Use Calculated Columns Wisely:
Minimise the use of calculated columns for performance reasons.
Reserve calculated columns for static, non-volatile data.
Implement Hierarchies:
Leverage hierarchies to enhance data drill-down capabilities.
Improves user experience and facilitates in-depth analysis.
Regularly Update Data:
Keep data refreshed to ensure the accuracy of your reports.
Schedule automatic refreshes based on your data update frequency.
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