PL-300 Model the data Practice Question
You have a Power BI model with a fact table 'Sales' and a dimension table 'Product'. The Product table contains columns: ProductID, ProductName, Category, and Subcategory. You want to create a hierarchy for drill-down in reports: Category > Subcategory > ProductName. What is the correct way to define this hierarchy?
⚠ Common exam trap
Watch out — candidates often confuse flattening data (merging or concatenating) with creating a true hierarchy, leading them to choose options B or C, which break drill-down functionality.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
In Model view, right-click 'Category' > 'Create hierarchy', then add Subcategory and ProductName as levels.
Power BI's Model view allows you to create a hierarchy by right-clicking a column (e.g., Category) and selecting 'Create hierarchy', then adding Subcategory and ProductName as child levels. This defines a natural drill-down path for visuals, enabling users to navigate from Category to Subcategory to ProductName without modifying the data model or using workarounds.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
In Model view, right-click 'Category' > 'Create hierarchy', then add Subcategory and ProductName as levels.
Why this is correct
This is the correct approach because a hierarchy created in Model view is a model-level object that explicitly defines parent-child relationships among the columns. Right-clicking Category and selecting 'Create hierarchy' places Category as the top level, after which you add Subcategory and ProductName as child levels, preserving each column's own granularity. A true hierarchy enables drill-down in visuals by expanding one level to the next, and it also supports functions like ISINSCOPE in DAX for level-aware calculations.
- ✗
In Power Query, merge the Category, Subcategory, and ProductName columns into one.
Why it's wrong here
Merging columns in Power Query flattens Category, Subcategory, and ProductName into a single delimited string expression, such as 'Bikes > Road > FRX-1'. This destroys the relational structure: there is no parent-child relationship in the data model, only one combined text attribute. Consequently, users cannot drill down level by level; they would have to parse the string to manually rebuild the levels, which is inefficient, error-prone, and loses the ability to filter or aggregate independently at each level.
- ✗
Create a calculated column using CONCATENATE to combine the levels.
Why it's wrong here
A calculated column using CONCATENATE (or the '&' operator) does exactly what the merge does in Power Query, but at the DAX layer: it creates a single scalar column with the combined text. From the model's perspective, this is not a hierarchy; it is just another attribute. No expansion or collapse behavior is defined, and the column cannot be used for drill-down unless users resort to text manipulation, which defeats the purpose of a structured hierarchy.
- ✗
In Report view, add all three columns to a visual's Values well.
Why it's wrong here
Adding the three columns to a visual's Values well (more commonly the Fields well) places independent columns side by side or in separate buckets in the visual, but it does not associate them as a hierarchy. In a table or matrix, they may appear as separate columns or rows, but there is no defined parent-child drill path, so drill-down functionality will not recognize a relationship. The correct pattern is to place a pre-built hierarchy in the Rows or Axis well, where the visual's built-in expand/collapse buttons can traverse levels.
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