Applied steps and undo in Power BI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a new applied step that filters rows where Sales is greater than 1000.

Power BI

let
    Source = Excel.CurrentWorkbook(){[Name="SalesData"]}[Content],
    FilteredRows = Table.SelectRows(Source, each [Sales] [1] 1000)
in
    FilteredRows

Drag options to blanks, or click blank then click option'

A<

B=

C>

D<=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' instead of '>' causes filtering of smaller values.

Using '=' filters only rows with Sales exactly 1000.

We use the greater than operator (>) to filter rows where Sales is more than 1000.

2fill in blank

medium

Complete the code to undo the last applied step by removing it from the steps list.

Power BI

let
    Source = Excel.CurrentWorkbook(){[Name="SalesData"]}[Content],
    RemovedLastStep = List.RemoveLastN(#"PreviousSteps", [1])
in
    RemovedLastStep

Drag options to blanks, or click blank then click option'

A1

B2

C0

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Removing 0 steps does nothing.

Removing more than 1 step removes too many steps.

Removing 1 step undoes the last applied step.

3fill in blank

hard

Fix the error in the code that tries to rename a column but uses the wrong function.

Power BI

let
    Source = Excel.CurrentWorkbook(){[Name="SalesData"]}[Content],
    RenamedColumns = Table.[1](Source, "OldName", "NewName")
in
    RenamedColumns

Drag options to blanks, or click blank then click option'

ARenameColumns

BRenameColumn

CRenameColumnNames

DRename

Attempts:

3 left

💡 Hint

Common Mistakes

Using singular form RenameColumn causes syntax error.

Using Rename is not a valid function.

The correct function to rename columns is Table.RenameColumns.

4fill in blank

hard

Fill both blanks to add a new applied step that changes the data type of the 'Date' column to date type.

Power BI

let
    Source = Excel.CurrentWorkbook(){[Name="SalesData"]}[Content],
    ChangedType = Table.[1](Source, [2])
in
    ChangedType

Drag options to blanks, or click blank then click option'

ATransformColumnTypes

BChangeType

DRenameColumns

Attempts:

3 left

💡 Hint

Common Mistakes

Using RenameColumns instead of changing type.

Using wrong argument format for the type change.

The correct function is Table.ChangeType and the second argument is a list of column-type pairs.

5fill in blank

hard

Fill all three blanks to add a step that filters rows where 'Region' equals 'West' and then undo that step.

Power BI

let
    Source = Excel.CurrentWorkbook(){[Name="SalesData"]}[Content],
    FilteredRows = Table.SelectRows(Source, each [[1]] = [2]),
    UndoStep = List.RemoveLastN([3], 1)
in
    UndoStep

Drag options to blanks, or click blank then click option'

ARegion

B"West"

C#"FilteredRows"

D#"Source"

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong column name or missing quotes around 'West'.

Undoing the wrong step by removing 'Source' instead of 'FilteredRows'.

We filter by 'Region' column equal to 'West', then undo by removing the last step which is 'FilteredRows'.

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