- A
CALCULATE(SUM(Sales[Amount]), PARALLELPERIOD('Date'[Date], -1, MONTH))
Why wrong: PARALLELPERIOD returns the same period offset, but it may return multiple months if the current period is not a single month; it's less precise.
- B
CALCULATE(SUM(Sales[Amount]), PREVIOUSMONTH('Date'[Date]))
PREVIOUSMONTH returns a set of dates for the previous month, and CALCULATE adjusts context.
- C
CALCULATE(SUM(Sales[Amount]), DATEADD('Date'[Date], -1, MONTH))
Why wrong: While DATEADD can also work, PREVIOUSMONTH is more idiomatic for prior month. However, this option is also correct in many scenarios, but the question expects PREVIOUSMONTH as the direct approach. Strictly, both are valid, but PREVIOUSMONTH is simpler.
- D
CALCULATE(SUM(Sales[Amount]), NEXTMONTH('Date'[Date]))
Why wrong: NEXTMONTH returns the next month, not previous.
Quick Answer
The answer is CALCULATE(SUM(Sales[Amount]), PREVIOUSMONTH('Date'[Date])). This expression is correct because PREVIOUSMONTH returns a contiguous set of dates representing the entire month immediately preceding the last date in the current filter context, and wrapping it inside CALCULATE shifts the filter on the Date table to that prior period, isolating the previous month’s sales. On the Microsoft Power BI Data Analyst PL-300 exam, this question tests your understanding of time intelligence functions and the necessity of a separate, continuous date table—a common trap is forgetting that PREVIOUSMONTH requires a date column from a proper date table, not the Sales table’s OrderDate. The search intent for “previous month sales dax” often trips candidates who try using DATEADD with -1 month, but PREVIOUSMONTH is more explicit for full-month periods. Memory tip: think “PREVIOUSMONTH pulls the month before the last date in view, not the month before today.”
PL-300 Model the data Practice Question
This PL-300 practice question tests your understanding of model the data. 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.
You have a Power BI model with a table named Sales that includes columns: OrderDate, Amount, and CustomerID. You need to create a measure that returns the total sales amount for the previous month based on the current filter context. Which DAX expression should you use?
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
CALCULATE(SUM(Sales[Amount]), PREVIOUSMONTH('Date'[Date]))
Option B is correct because PREVIOUSMONTH returns a single month period shifted back by one month from the last date in the current filter context, which directly gives the total sales for the previous month. This measure respects the current filter context and works correctly when a proper date table is used.
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.
- ✗
CALCULATE(SUM(Sales[Amount]), PARALLELPERIOD('Date'[Date], -1, MONTH))
Why it's wrong here
PARALLELPERIOD returns the same period offset, but it may return multiple months if the current period is not a single month; it's less precise.
- ✓
CALCULATE(SUM(Sales[Amount]), PREVIOUSMONTH('Date'[Date]))
Why this is correct
PREVIOUSMONTH returns a set of dates for the previous month, and CALCULATE adjusts context.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
CALCULATE(SUM(Sales[Amount]), DATEADD('Date'[Date], -1, MONTH))
Why it's wrong here
While DATEADD can also work, PREVIOUSMONTH is more idiomatic for prior month. However, this option is also correct in many scenarios, but the question expects PREVIOUSMONTH as the direct approach. Strictly, both are valid, but PREVIOUSMONTH is simpler.
- ✗
CALCULATE(SUM(Sales[Amount]), NEXTMONTH('Date'[Date]))
Why it's wrong here
NEXTMONTH returns the next month, not previous.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse PREVIOUSMONTH with DATEADD or PARALLELPERIOD, not realizing that PREVIOUSMONTH is specifically designed to return a single full previous month based on the last date in context, while DATEADD shifts dates individually and PARALLELPERIOD can return multiple periods.
Trap categories for this question
Scenario analysis trap
While DATEADD can also work, PREVIOUSMONTH is more idiomatic for prior month. However, this option is also correct in many scenarios, but the question expects PREVIOUSMONTH as the direct approach. Strictly, both are valid, but PREVIOUSMONTH is simpler.
Detailed technical explanation
How to think about this question
PREVIOUSMONTH is a time intelligence function that relies on a contiguous date table marked as a date table in Power BI. It internally uses the last date in the current filter context to define the previous month boundary, ensuring that all dates in that month are included. A common pitfall is forgetting to mark the date table properly, which causes PREVIOUSMONTH to return blank or incorrect results.
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.
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FAQ
Questions learners often ask
What does this PL-300 question test?
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[Amount]), PREVIOUSMONTH('Date'[Date])) — Option B is correct because PREVIOUSMONTH returns a single month period shifted back by one month from the last date in the current filter context, which directly gives the total sales for the previous month. This measure respects the current filter context and works correctly when a proper date table is used.
What should I do if I get this PL-300 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jun 24, 2026
This PL-300 practice question is part of Courseiva's free Microsoft certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PL-300 exam.
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