Removing duplicates in Power BI - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to remove duplicate rows from the table.

Power BI

DistinctTable = DISTINCT([1])

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

ASUMMARIZE

BFILTER

CSales

DVALUES

Attempts:

3 left

💡 Hint

Common Mistakes

Using a function like SUMMARIZE instead of a table name.

Passing a column name instead of a table.

The DISTINCT function removes duplicate rows from the specified table. Here, we use the table name Sales as input.

2fill in blank

medium

Complete the code to create a table with unique CustomerIDs from Sales.

Power BI

UniqueCustomers = VALUES([1][CustomerID])

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

AProducts

BOrders

CCustomers

DSales

Attempts:

3 left

💡 Hint

Common Mistakes

Using a table that does not have the CustomerID column.

Using DISTINCT instead of VALUES (DISTINCT requires a table expression, not a column).

The VALUES function returns unique values from the specified column. Here, we want unique CustomerIDs from the Sales table.

3fill in blank

hard

Fix the error in the code to remove duplicates from the Sales table.

Power BI

CleanSales = DISTINCT([1])

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

ASales

BSUMMARIZE(Sales, Sales[CustomerID])

CSales[Amount]

DFILTER(Sales, Sales[Amount] > 0)

Attempts:

3 left

💡 Hint

Common Mistakes

Passing a column like Sales[Amount] instead of the whole table.

Using functions inside DISTINCT that return tables but are not needed.

DISTINCT requires a table as input. Using Sales (the table) is correct. Passing a column causes an error; other options use unnecessary table expressions.

4fill in blank

hard

Fill both blanks to create a table with unique CustomerIDs from Sales.

Power BI

UniqueCombos = SUMMARIZE([1], [2])

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

ASales

BSales[CustomerID]

CSales[ProductID]

DProducts

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different table than Sales.

Using a column from a different table.

The SUMMARIZE function groups the Sales table by Sales[CustomerID] to get unique CustomerIDs.

5fill in blank

hard

Fill all three blanks to create a table with unique CustomerID and ProductID combinations using SUMMARIZE.

Power BI

UniqueCombos = SUMMARIZE([1], [2], [3])

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

ASales

BSales[CustomerID]

CSales[ProductID]

DCustomers

Attempts:

3 left

💡 Hint

Common Mistakes

Using columns from different tables.

Using a table other than Sales.

SUMMARIZE groups the Sales table by CustomerID and ProductID columns to remove duplicates of these combinations.

Practice

1. What is the main purpose of removing duplicates in Power BI data?

easy

A. To add more rows to the dataset

B. To keep data clean and reliable by eliminating repeated rows

C. To change the data types of columns

D. To create new calculated columns

Solution

1. Step 1: Understand the concept of duplicates

   Duplicates are repeated rows that can cause errors or confusion in analysis.

2. Step 2: Purpose of removing duplicates

   Removing duplicates ensures the data is clean and reliable for accurate reporting.

3. Final Answer:

   To keep data clean and reliable by eliminating repeated rows -> Option B

4. Quick Check:

   Removing duplicates = Clean data [OK]

Hint: Duplicates cause errors; removing them cleans data fast [OK]

Common Mistakes:

• Thinking duplicates add useful data
• Confusing duplicates with data transformation
• Believing duplicates change data types

2. Which of the following is the correct syntax to remove duplicate rows from a table named Sales in Power Query?

easy

A. Table.RemoveDuplicates(Sales)

B. Remove.Duplicates(Sales)

C. Table.Distinct(Sales)

D. DistinctRows(Sales)

Solution

1. Step 1: Recall Power Query function for duplicates

   The correct function to remove duplicates is Table.Distinct.

2. Step 2: Apply function to the table

   Using Table.Distinct(Sales) removes duplicate rows from the Sales table.

3. Final Answer:

   Table.Distinct(Sales) -> Option C

4. Quick Check:

   Table.Distinct = Remove duplicates [OK]

Hint: Use Table.Distinct to remove duplicates in Power Query [OK]

Common Mistakes:

• Using non-existent functions like Remove.Duplicates
• Confusing syntax with other languages
• Adding extra parameters unnecessarily

3. Given the table Customers with columns CustomerID and City, what will be the result of Table.Distinct(Customers, {"CustomerID"})?

medium

A. Removes duplicate rows based on all columns

B. Removes duplicate rows based only on City column

C. Returns the original table without changes

D. Removes duplicate rows based only on CustomerID column

Solution

1. Step 1: Understand Table.Distinct with column list

   When columns are specified, duplicates are removed based on those columns only.

2. Step 2: Apply to CustomerID column

   Here, duplicates are removed based on CustomerID, ignoring other columns.

3. Final Answer:

   Removes duplicate rows based only on CustomerID column -> Option D

4. Quick Check:

   Distinct by columns = Remove duplicates by those columns [OK]

Hint: Specify columns in Table.Distinct to target duplicates [OK]

Common Mistakes:

• Assuming all columns are checked when columns are specified
• Confusing column names in the list
• Thinking it returns unchanged table

4. You wrote Table.Distinct(Sales, "ProductID") to remove duplicates by ProductID but get an error. What is the likely problem?

medium

A. The second argument should be a list of column names, not a single string

B. Table.Distinct does not accept a second argument

C. ProductID column does not exist in Sales table

D. You must use Table.RemoveDuplicates instead

Solution

1. Step 1: Check Table.Distinct syntax for columns

   The second argument must be a list of column names, e.g., {"ProductID"}, not a string.

2. Step 2: Identify error cause

   Passing "ProductID" as a string causes a syntax error because it expects a list.

3. Final Answer:

   The second argument should be a list of column names, not a single string -> Option A

4. Quick Check:

   Columns argument = List, not string [OK]

Hint: Use curly braces {} for column list in Table.Distinct [OK]

Common Mistakes:

• Passing column name as string instead of list
• Using wrong function name
• Assuming single argument works for columns

5. You have a table Orders with columns OrderID, CustomerID, and OrderDate. You want to keep only the first order per customer by date, removing duplicates of CustomerID but keeping the earliest OrderDate. Which approach is best in Power Query?

hard

A. Sort Orders by OrderDate ascending, then use Table.Distinct(Orders, {"CustomerID"})

B. Use Table.Distinct(Orders, {"CustomerID", "OrderDate"}) without sorting

C. Remove duplicates by OrderID column

D. Filter Orders to keep only rows where OrderDate is max per CustomerID

Solution

1. Step 1: Sort Orders by OrderDate ascending

   Sorting ensures earliest dates come first for each customer.

2. Step 2: Remove duplicates by CustomerID

   Using Table.Distinct(Orders, {"CustomerID"}) keeps the first row per customer, which is earliest due to sorting.

3. Final Answer:

   Sort Orders by OrderDate ascending, then use Table.Distinct(Orders, {"CustomerID"}) -> Option A

4. Quick Check:

   Sort then distinct = keep earliest per group [OK]

Hint: Sort by date first, then remove duplicates by customer [OK]

Common Mistakes:

• Removing duplicates without sorting first
• Including OrderDate in distinct columns
• Filtering by max date instead of min