Applied steps and undo in Power BI - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding Applied Steps Order

In Power BI's Query Editor, you apply several transformation steps to your data. If you want to remove the third step you applied, what happens to the steps that come after it?

A All steps after the removed step are also removed.

B Only the removed step is deleted; later steps remain unchanged.

C The removed step is disabled but still affects later steps.

D The entire query is reset to the original data.

💡 Hint

Think about how each step depends on the previous one.

In Power BI, each applied step builds on the previous one. Removing a step breaks the chain, so all steps after it are removed to avoid errors.

🎯 Scenario

intermediate

Undoing Changes in Query Editor

You accidentally applied a filter step that removed important rows. Which method allows you to undo this change without closing the Query Editor?

A Right-click the table and select 'Refresh Data'.

B Close the Query Editor without saving and reopen the file.

C Click the 'X' next to the filter step in the Applied Steps pane.

D Use the Undo button in the Home ribbon to revert all changes.

💡 Hint

Look for a way to remove a specific step directly.

Clicking the 'X' next to a step removes that step and all dependent steps, effectively undoing that change.

🔧 Formula Fix

advanced

Fixing a Broken Query After Undo

After removing an applied step in Power BI Query Editor, the query shows an error. What is the most likely cause?

A Power BI requires a restart after removing any applied step.

B The data source connection was lost during the undo operation.

C Undoing a step automatically deletes the entire query.

D Later steps depend on the removed step and now reference missing data.

💡 Hint

Think about dependencies between steps.

Removing a step breaks the chain for later steps that rely on it, causing errors until fixed.

❓ visualization

advanced

Visualizing Applied Steps Impact

You want to create a dashboard visualization showing how many applied steps each query in your Power BI report has. Which visual and measure combination is best?

A Use a table visual listing queries with a measure counting applied steps per query.

B Use a pie chart showing the total number of applied steps across all queries.

C Use a line chart showing applied steps count over time for each query.

D Use a card visual showing the average applied steps for all queries.

💡 Hint

Think about showing details per query clearly.

A table visual with a count measure per query clearly shows applied steps per query, making it easy to compare.

❓ data_modeling

expert

Managing Applied Steps for Performance Optimization

You have a complex query with many applied steps causing slow refresh times. Which approach best improves performance without losing data transformation accuracy?

A Disable query folding to force all transformations locally.

B Combine multiple transformation steps into fewer steps using advanced M code.

C Remove all applied steps and load raw data, then transform in DAX measures.

D Duplicate the query and apply transformations twice for safety.

💡 Hint

Think about reducing complexity while keeping transformations accurate.

Combining steps reduces overhead and improves refresh speed while preserving transformations.

Practice

1. What is the main purpose of Applied Steps in Power BI's Query Editor?

easy

A. To write DAX formulas for calculations

B. To create visualizations automatically

C. To track and record every change made to the data during cleaning

D. To connect Power BI to external databases

Solution

1. Step 1: Understand Applied Steps function

   Applied Steps record each transformation or change you make to your data in Query Editor.

2. Step 2: Differentiate from other features

   Applied Steps do not create visuals, write formulas, or connect databases; they track data cleaning actions.

3. Final Answer:

   To track and record every change made to the data during cleaning -> Option C

4. Quick Check:

   Applied Steps = Track changes [OK]

Hint: Applied Steps = your data cleaning history [OK]

Common Mistakes:

• Confusing Applied Steps with visualization features
• Thinking Applied Steps write formulas
• Assuming Applied Steps connect to databases

2. Which of the following is the correct way to undo the last applied step in Power BI Query Editor?

easy

A. Click the 'X' next to the last step in the Applied Steps pane

B. Press Ctrl + Z anywhere in Power BI Desktop

C. Delete the entire query and start over

D. Right-click the data table and select 'Undo'

Solution

1. Step 1: Locate Applied Steps pane

   The Applied Steps pane shows each change; each step has an 'X' to remove it.

2. Step 2: Undo last step by removing it

   Clicking the 'X' next to the last step removes that change, effectively undoing it.

3. Final Answer:

   Click the 'X' next to the last step in the Applied Steps pane -> Option A

4. Quick Check:

   Undo last step = Click 'X' [OK]

Hint: Undo last step by clicking 'X' in Applied Steps [OK]

Common Mistakes:

• Using Ctrl + Z which doesn't undo Query Editor steps
• Deleting entire query unnecessarily
• Looking for undo option outside Applied Steps

3. Given these Applied Steps in Power BI Query Editor:
1. Source
2. Removed Columns
3. Filtered Rows

If you click the 'X' next to Removed Columns, what will happen?

medium

A. Both 'Removed Columns' and 'Filtered Rows' steps will be deleted

B. 'Removed Columns' step will be deleted, and 'Filtered Rows' will be recalculated without it

C. Only 'Filtered Rows' step will be deleted

D. Nothing will change because you cannot delete middle steps

Solution

1. Step 1: Understand step dependencies

   Deleting a middle step removes that transformation; later steps recalculate based on remaining steps.

2. Step 2: Effect on later steps

   'Filtered Rows' depends on the data after 'Removed Columns'; it will recalculate using data without that removal.

3. Final Answer:

   'Removed Columns' step will be deleted, and 'Filtered Rows' will be recalculated without it -> Option B

4. Quick Check:

   Deleting middle step recalculates later steps [OK]

Hint: Deleting a step recalculates all following steps [OK]

Common Mistakes:

• Assuming all later steps delete automatically
• Thinking middle steps cannot be deleted
• Believing nothing changes after deletion

4. You accidentally removed a column in Power BI Query Editor but did not want to. Which of these is the best way to fix it?

medium

A. Create a new query from scratch

B. Close Power BI without saving and reopen the file

C. Manually add the column back using DAX

D. Undo the removal by deleting the 'Removed Columns' step in Applied Steps

Solution

1. Step 1: Identify the mistake step

   The 'Removed Columns' step is where the column was removed.

2. Step 2: Undo by deleting the step

   Deleting this step in Applied Steps will restore the column as if it was never removed.

3. Final Answer:

   Undo the removal by deleting the 'Removed Columns' step in Applied Steps -> Option D

4. Quick Check:

   Undo mistake by deleting step [OK]

Hint: Fix mistakes by deleting wrong Applied Steps [OK]

Common Mistakes:

• Closing without saving loses all work
• Trying to add columns with DAX instead of Query Editor
• Rebuilding query unnecessarily

5. You applied these steps in order:
1. Changed Type
2. Filtered Rows
3. Added Custom Column

Later you realize the 'Changed Type' step was incorrect. What is the best approach to fix this without losing your custom column?

hard

A. Delete the 'Changed Type' step and then reapply it correctly before the other steps

B. Delete all steps and start over from the source

C. Edit the 'Added Custom Column' step to fix the type issue

D. Ignore the error and proceed with the current steps

Solution

1. Step 1: Remove incorrect 'Changed Type' step

   Delete the wrong 'Changed Type' step to remove the incorrect data type changes.

2. Step 2: Reapply correct 'Changed Type' step before other steps

   Reapply the correct type changes before 'Filtered Rows' and 'Added Custom Column' to keep data consistent.

3. Final Answer:

   Delete the 'Changed Type' step and then reapply it correctly before the other steps -> Option A

4. Quick Check:

   Fix errors by correcting early steps without losing later ones [OK]

Hint: Fix early step errors by deleting and reapplying them [OK]

Common Mistakes:

• Deleting all steps loses work
• Editing later steps to fix early errors
• Ignoring errors causes wrong data