Power BI 778 Power Query and Data Transformation 2 — Questions and Answers
Question 1: What does the 'Group By' transformation do in Power Query?
- Sorts rows by a specified column
- Aggregates rows based on one or more grouping columns (Correct answer)
- Filters rows by a category value
- Splits one column into multiple columns
Correct answer: Aggregates rows based on one or more grouping columns
Group By in Power Query aggregates data by specified columns, similar to GROUP BY in SQL.
Question 2: What is a 'Reference' query in Power Query?
- A query that imports data from a reference table
- A query that uses another query as its source without duplicating the data load (Correct answer)
- A query that references an external API
- A query that stores credentials for data sources
Correct answer: A query that uses another query as its source without duplicating the data load
A Reference query points to another query as its starting point, sharing the same data load without running the source query twice.
Question 3: What does 'Fill Down' do in Power Query?
- Replaces null values with the value from the cell above in the same column (Correct answer)
- Copies the last row's values to all empty rows
- Fills blank cells with zeros
- Propagates a formula down a column
Correct answer: Replaces null values with the value from the cell above in the same column
Fill Down replaces null values in a column by carrying forward the most recent non-null value from the rows above.
Question 4: Which Power Query transformation splits a column into multiple columns based on a delimiter?
- Extract
- Parse
- Split Column (Correct answer)
- Pivot Column
Correct answer: Split Column
Split Column divides a column into multiple columns using a specified delimiter like a comma, space, or custom character.
Question 5: What is query folding in Power Query?
- Collapsing multiple queries into one for performance
- Pushing transformation steps back to the data source to execute natively (Correct answer)
- Hiding intermediate query steps from the applied steps pane
- Combining queries from different workspaces
Correct answer: Pushing transformation steps back to the data source to execute natively
Query folding allows Power Query to translate transformation steps into native source queries (e.g., SQL), improving performance by reducing data transferred.
Question 6: What does the 'Pivot Column' transformation do in Power Query?
- Converts attribute-value rows into separate columns (Correct answer)
- Rotates rows into columns based on a key column
- Aggregates a column into a single value
- Converts a column to a different data type
Correct answer: Converts attribute-value rows into separate columns
Pivot Column turns unique values from one column into new column headers, essentially transposing key-value pairs into a wide table.
Power BI 778 Power Query and Data Transformation 2
What does the 'Group By' transformation do in Power Query?