Reducing loaded data in Power Query with grouping and column removal

Transform and load the data
Answer Correct answer: A, C — grouping to the needed grain and removing unused columns and rows are the documented data-reduction techniques.

You have a Power BI semantic model that contains two queries. You discover that a report based on the model has performance issues. You plan to use Power Query to reduce the data loaded to the model. Which two actions should you perform? Each correct answer presents part of the solution. NOTE: Each correct answer is worth one point.

  1. Apply group by and summarize techniques. Correct Answer
  2. Combine the queries by using Append.
  3. Remove unnecessary columns and rows. Correct Answer
  4. Combine the queries by using Merge.
  5. Create a new query group.
data reduction power query group by summarize remove unnecessary columns

Community Votes

AC
100%

100% of anonymous learners picked answer AC. Votes are pick records left by other test-takers — they are not the verified answer.

Community Insight

Microsoft's data-reduction guidance names exactly these levers: remove unnecessary columns and rows before load, and group or summarize detail to the grain the report actually needs.

A report on a two-query semantic model underperforms, and Power Query must be used to cut the data volume loaded into the model, with two complementary actions to pick.

Treating query consolidation as data reduction — Append and Merge change how tables come together (and often grow row or column counts), while query groups are pure authoring hygiene with zero effect on model size.

Community Discussion (5 comments)

desibaby09 👍 2 Selected: AC
https://learn.microsoft.com/en-us/power-bi/guidance/import-modeling-data-reduction
jaume 👍 2 Selected: AC
Ony options A and C will reduce data size and potentially improving performance. Combining queries (by using Append or Merge) could improve refresh but not report performance as is and a new query group would not impact at all
amiruladliroslibin 👍 3 Selected: AC
B. Combine the queries by using Append While combining queries via append can help merge multiple datasets, it typically does not reduce the data size. In fact, it may increase the dataset size unless managed carefully. D. Combine the queries by using Merge Merging queries is useful for joining data from different sources, but it is not inherently a data reduction technique. It may help in certain cases, but it is not directly aimed at reducing the amount of data loaded to the model. E. Create a new query group A query group is simply an organizational tool in Power Query to manage your queries better. It has no impact on performance or data reduction.
LuluSkyy 👍 2
A and C are the correct answers
VladStan 👍 4 Selected: AC
Correct answers https://learn.microsoft.com/en-us/power-bi/guidance/import-modeling-data-reduction

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Expert Analysis

Why the Answer Is Correct

Applying group by and summarize techniques (A) collapses detail rows to a higher grain before load, directly shrinking fact tables — the official data-reduction guidance for import models lists grouping and aggregating as a first-line technique. Removing unnecessary columns and rows (C) eliminates fields and records no visual consumes, which reduces both the dataset size and refresh load. Microsoft's import modeling guidance names column and row removal as the most effective data reduction step.

Why the Other Options Are Wrong

Appending queries (B) stacks tables into more rows, growing rather than shrinking the model. Merging queries (D) adds lookup columns to a table, increasing column count unless other reductions follow — on its own it reduces nothing. Creating a new query group (E) merely organizes queries in the editor's folder tree; the data loaded is byte-identical.

Community Comment Notes

Several commenters anchor A and C to the official import-modeling-data-reduction guidance page. One adds the useful observation that Append can actually increase dataset size, and that a query group only affects Power Query editor organization.

Official Reference

https://learn.microsoft.com/en-us/power-bi/guidance/import-modeling-data-reduction

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