Power BI 778 Power Query and Data Transformation 1 — Questions and Answers
Question 1: What is Power Query used for in Power BI?
- Writing DAX measures
- Connecting to data sources and transforming data before loading (Correct answer)
- Creating visualizations
- Publishing reports to the Power BI Service
Correct answer: Connecting to data sources and transforming data before loading
Power Query is the ETL (Extract, Transform, Load) engine in Power BI used to connect, clean, and shape data before analysis.
Question 2: What language do Power Query transformations use behind the scenes?
- DAX
- SQL
- M (Power Query Formula Language) (Correct answer)
- Python
Correct answer: M (Power Query Formula Language)
Power Query uses M language, a functional language that defines every transformation step applied to your data.
Question 3: Which Power Query step removes rows where a specified column's value is null?
- Remove Duplicates
- Filter Rows (Correct answer)
- Remove Errors
- Fill Down
Correct answer: Filter Rows
Filter Rows allows you to filter out rows based on conditions, including removing rows where a column value is null.
Question 4: What does 'Append Queries' do in Power Query?
- Merges two tables by matching on a key column
- Stacks rows from multiple tables vertically into one table (Correct answer)
- Joins two tables side by side
- Removes duplicate rows across tables
Correct answer: Stacks rows from multiple tables vertically into one table
Append Queries combines tables by stacking their rows on top of each other, similar to UNION ALL in SQL.
Question 5: What does 'Merge Queries' do in Power Query?
- Stacks rows from two tables vertically
- Joins two tables horizontally on a common key column (Correct answer)
- Combines all columns from all tables
- Removes matching rows from one table
Correct answer: Joins two tables horizontally on a common key column
Merge Queries performs a join between two tables based on matching key columns, similar to a SQL JOIN.
Question 6: What is the purpose of the 'Unpivot Columns' transformation in Power Query?
- Converts row data into column headers
- Converts multiple columns into attribute-value row pairs (Correct answer)
- Removes selected columns from a table
- Transposes rows and columns
Correct answer: Converts multiple columns into attribute-value row pairs
Unpivot Columns rotates selected columns into rows, creating an attribute column and a value column for each combination.
Power BI 778 Power Query and Data Transformation 1
What is Power Query used for in Power BI?