The answer is that the date table is not marked as a date table in Power BI. This is the most likely cause because time intelligence functions like SAMEPERIODLASTYEAR rely on a continuous, properly defined date hierarchy to shift context; without marking the table, Power BI cannot guarantee that every date in the measure’s filter context has a corresponding prior-year match, so it returns blank for months where the date lineage is broken. On the Microsoft Power Platform Fundamentals PL-900 exam, this tests your understanding of data modeling prerequisites for DAX time intelligence—a common trap is assuming that any date column works, but the engine requires an explicit “Mark as Date Table” step to enable calendar logic. A quick memory tip: think of it as “No mark, no spark”—if you don’t mark the date table, SAMEPERIODLASTYEAR won’t fire correctly.
PL-900 Practice Question: Describe the business value of Microsoft Power Platform
This PL-900 practice question tests your understanding of describe the business value of microsoft power platform. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
Exhibit
Refer to the exhibit.
```dax
Sales Growth % =
DIVIDE(
SUM(Sales[Amount]) - CALCULATE(SUM(Sales[Amount]), SAMEPERIODLASTYEAR(Date[Date])),
CALCULATE(SUM(Sales[Amount]), SAMEPERIODLASTYEAR(Date[Date]))
) * 100
```
A Power BI report shows a measure 'Sales Growth %' defined as above. The measure returns blank for some months even though sales data exists. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The date table is not marked as a date table in Power BI.
When a date table is not marked as a date table in Power BI, time intelligence functions like SAMEPERIODLASTYEAR may not correctly identify the date context, causing them to return blank for certain periods even when data exists. Marking the table as a date table ensures that Power BI uses its built-in date hierarchy and calendar logic, which is required for functions that shift or compare date ranges.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
The date table is not marked as a date table in Power BI.
Why this is correct
Time intelligence functions require a marked date table with continuous dates.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The measure should use TOTALYTD instead of SAMEPERIODLASTYEAR.
Why it's wrong here
TOTALYTD is for year-to-date, not same period last year.
✗
The Sales table has no relationship with the Date table.
Why it's wrong here
If no relationship, SAMEPERIODLASTYEAR would still return blank, but a relationship is needed.
✗
The DIVIDE function requires a third argument for alternate result.
Why it's wrong here
DIVIDE without third argument returns BLANK when denominator is zero, but here denominator may be blank.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume the blank result is due to missing data or a broken relationship, when in fact the root cause is that the date table is not properly configured to support time intelligence functions.
Detailed technical explanation
How to think about this question
Under the hood, time intelligence functions rely on a contiguous, complete date table marked with a continuous date range. If the table is not marked, Power BI cannot guarantee that all dates in the filter context are present, so SAMEPERIODLASTYEAR may fail to find the corresponding prior period for months where the date table lacks a full set of dates or where the relationship is not recognized as a date hierarchy. In real-world scenarios, this often occurs when a date table is imported from a source that does not include all dates (e.g., only business days) or when the table’s date column contains gaps, causing the function to return blank for months that fall outside the defined date range.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Describe the business value of Microsoft Power Platform — This question tests Describe the business value of Microsoft Power Platform — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The date table is not marked as a date table in Power BI. — When a date table is not marked as a date table in Power BI, time intelligence functions like SAMEPERIODLASTYEAR may not correctly identify the date context, causing them to return blank for certain periods even when data exists. Marking the table as a date table ensures that Power BI uses its built-in date hierarchy and calendar logic, which is required for functions that shift or compare date ranges.
What should I do if I get this PL-900 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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