- A
Remove the RELATED function and merge tables in the source query.
Why wrong: This could work but requires changing the data source query, which may not be under the report developer's control.
- B
Convert the model to Import mode.
Why wrong: Converting to Import mode would improve performance but changes the data refresh strategy; the question asks for a design change without compromising functionality, and import requires scheduled refresh, which may not be acceptable.
- C
Use a measure instead of a calculated column.
Why wrong: Measures are evaluated at query time and may not solve the performance issue; they might even be slower if they need to compute row context.
- D
Replace the calculated column with a calculated table that includes the related column.
A calculated table is materialized in the model, reducing query-time computation and improving performance.
Quick Answer
The correct design change is to replace the calculated column with a calculated table that includes the related column. This improves performance because in DirectQuery mode, calculated columns are evaluated row-by-row at query time, and using the RELATED function in a column forces a separate lookup per row, creating significant overhead. A calculated table, by contrast, is resolved as a single query to the source during refresh, moving the join logic to the database and eliminating repeated row-level lookups. On the PL-300 exam, this scenario tests your understanding of DirectQuery optimization trade-offs—a common trap is assuming all calculated objects behave the same, when in fact calculated tables avoid the per-row penalty of calculated columns. Remember the mnemonic: “Tables are batched, columns are per-row—when DirectQuery is slow, batch the join.”
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.
A Power BI report uses a DirectQuery data source. The model includes a calculated column that uses the RELATED function to bring a value from another table. The report is performing slowly. What design change would most improve performance without compromising 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
Replace the calculated column with a calculated table that includes the related column.
Option D is correct because replacing the calculated column with a calculated table that includes the related column moves the join logic to query time, reducing the per-row overhead of the RELATED function in DirectQuery mode. In DirectQuery, calculated columns are evaluated row-by-row for each query, which can cause significant performance degradation; a calculated table is materialized once during refresh (or in DirectQuery, it is resolved as a single query to the source), avoiding repeated row-level lookups. This change preserves the functionality of having the related value available in the table while improving query performance.
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.
- ✗
Remove the RELATED function and merge tables in the source query.
Why it's wrong here
This could work but requires changing the data source query, which may not be under the report developer's control.
- ✗
Convert the model to Import mode.
Why it's wrong here
Converting to Import mode would improve performance but changes the data refresh strategy; the question asks for a design change without compromising functionality, and import requires scheduled refresh, which may not be acceptable.
- ✗
Use a measure instead of a calculated column.
Why it's wrong here
Measures are evaluated at query time and may not solve the performance issue; they might even be slower if they need to compute row context.
- ✓
Replace the calculated column with a calculated table that includes the related column.
Why this is correct
A calculated table is materialized in the model, reducing query-time computation and improving performance.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume measures are always faster than calculated columns, but in DirectQuery, measures cannot replace columns needed for row-level operations, and the real performance gain comes from avoiding row-by-row evaluation by using a calculated table instead.
Detailed technical explanation
How to think about this question
In DirectQuery mode, calculated columns are translated into SQL subqueries that execute the RELATED function as a correlated subquery for each row, which can lead to N+1 query patterns and poor performance. A calculated table, on the other hand, is materialized as a single query (e.g., a JOIN in the source database) and cached in the model, reducing round trips. However, note that in DirectQuery, calculated tables are still resolved at query time and not stored in memory, but they avoid the per-row overhead by performing the join once in the generated SQL.
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: Replace the calculated column with a calculated table that includes the related column. — Option D is correct because replacing the calculated column with a calculated table that includes the related column moves the join logic to query time, reducing the per-row overhead of the RELATED function in DirectQuery mode. In DirectQuery, calculated columns are evaluated row-by-row for each query, which can cause significant performance degradation; a calculated table is materialized once during refresh (or in DirectQuery, it is resolved as a single query to the source), avoiding repeated row-level lookups. This change preserves the functionality of having the related value available in the table while improving query performance.
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.
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Last reviewed: Jun 11, 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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