PL-300 · Question #452
You have a Power BI semantic model that contains the following data. You need to create a solution that meets the following requirements: - Presents transaction amount totals for each month for the…
The correct answer is A. Create one-to-many relationships between the tables. B. In the Transactions query, delete the TransactionID column. D. In the Transactions query, group by AccountID and MonthStartDate for TransactionDate. To model transaction totals by month and year using a star schema while minimizing model size, establish one-to-many relationships, remove unnecessary columns, and pre-aggregate the fact data to the desired grain.
Question
You have a Power BI semantic model that contains the following data. You need to create a solution that meets the following requirements:
- Presents transaction amount totals for each month for the current and
prior year
- Follows the star schema modeling approach
- Minimizes the data model size
Which three actions should you perform? Each correct answer presents part of the solution. NOTE: Each correct selection is worth one point.
Options
- ACreate one-to-many relationships between the tables.
- BIn the Transactions query, delete the TransactionID column.
- CIn the Date query, group by MonthNumber.
- DIn the Transactions query, group by AccountID and MonthStartDate for TransactionDate.
- EIn the Transactions query, add a column that contains the MonthStartDate value for
- FCreate many-to-many relationships between the tables.
How the community answered
(45 responses)- A84% (38)
- C2% (1)
- E4% (2)
- F9% (4)
Why each option
To model transaction totals by month and year using a star schema while minimizing model size, establish one-to-many relationships, remove unnecessary columns, and pre-aggregate the fact data to the desired grain.
Creating one-to-many relationships between dimension tables (like Date and Account) and the fact table (Transactions) is fundamental to a star schema, enabling efficient filtering and aggregation for the required analysis.
In the Transactions query, deleting the TransactionID column minimizes data model size because it is a unique identifier typically not used for analysis or aggregation, thus reducing the number of high-cardinality columns in the fact table.
In the Date query, grouping by MonthNumber would simplify the date dimension but would lose specific date information (like year), which is needed to present data for the current and prior year, and it's not a standard practice for creating a robust date dimension.
In the Transactions query, grouping by AccountID and MonthStartDate for TransactionDate and summing the Amount effectively pre-aggregates the fact data to the required grain (monthly totals per account), significantly reducing the number of rows in the fact table and thus model size.
In the Transactions query, adding a column that contains the MonthStartDate value for TransactionDate would add a redundant column if a proper Date dimension is used and related, and it does not reduce model size; it potentially increases it.
Creating many-to-many relationships violates the star schema modeling approach, which primarily relies on one-to-many relationships between dimension and fact tables for optimal performance and simplicity.
Concept tested: Star schema design, data model optimization, Power Query transformations
Source: https://learn.microsoft.com/en-us/power-bi/guidance/star-schema
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