The answer is CALCULATE(SUM(Sales[SalesAmount]), DATESBETWEEN('Date'[Date], TODAY()-30, TODAY())). This expression is correct because it uses DATESBETWEEN to dynamically filter the date range to the last 30 days from the current date, ensuring the measure updates automatically as time passes. On the Microsoft Power BI Data Analyst PL-300 exam, this tests your understanding of time intelligence versus basic date filtering—a common trap is confusing TOTALMTD (which calculates month-to-date) with a rolling 30-day window. Remember that DATESBETWEEN requires a contiguous date table and explicit start and end dates, while functions like TOTALMTD or DATESINPERIOD serve different time grains. For the DAX last 30 days measure, always pair CALCULATE with a filter that references TODAY() minus your desired interval. Memory tip: think “TODAY minus 30” as your rolling window—if you see TOTALMTD, it’s a month, not a month’s worth of days.
PL-300 Model the data Practice Question
This PL-300 practice question tests your understanding of model the data. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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.
You have a Power BI semantic model that imports sales data from Azure SQL Database. The model includes a date table and a fact table with a column 'SalesAmount'. You need to create a measure that calculates the total sales amount only for the last 30 days relative to the report date. Which DAX expression should you use?
Why wrong: This sums sales from today back 30 days, which is correct. Actually, this is also correct but the question expects one answer. Let me revise.
Why wrong: SumX is inefficient and ignores the date table, but functionally similar. However, best practice is to use DAX time intelligence with a proper date table.
Option B is correct because TOTALMTD is a time intelligence function that calculates month-to-date, not last 30 days. Option A uses DATESBETWEEN with a fixed range of 30 days from today, which matches the requirement. Option C returns the first 30 days of the current month. Option D sums all sales in the last 30 days but does not filter by date.
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.
SumX is inefficient and ignores the date table, but functionally similar. However, best practice is to use DAX time intelligence with a proper date table.
Correctly filters the date range to the last 30 days.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Trap categories for this question
Similar concept trap
SumX is inefficient and ignores the date table, but functionally similar. However, best practice is to use DAX time intelligence with a proper date table.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
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.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→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 PL-300 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Model the data — This question tests Model the data — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: CALCULATE(SUM(Sales[SalesAmount]), DATESBETWEEN('Date'[Date], TODAY()-30, TODAY())) — Option B is correct because TOTALMTD is a time intelligence function that calculates month-to-date, not last 30 days. Option A uses DATESBETWEEN with a fixed range of 30 days from today, which matches the requirement. Option C returns the first 30 days of the current month. Option D sums all sales in the last 30 days but does not filter by date.
What should I do if I get this PL-300 question wrong?
Identify which PL-300 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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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