PL-300 Prepare the data Practice Question
Which TWO options are valid methods to combine multiple tables in Power Query?
⚠ Common exam trap
Watch out — candidates often confuse SQL terminology (Join, Union) with Power Query's specific functions (Merge, Append), leading them to select the generic terms instead of the correct Power Query operations.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Merge
In Power Query, Merge is the correct operation for combining two tables horizontally by matching rows on one or more key columns, equivalent to a SQL JOIN, and it is performed via Home > Merge Queries. Append is the correct operation for stacking tables vertically, adding the rows of one table beneath another, equivalent to SQL UNION ALL, and it is performed via Home > Append Queries. The other options are not Power Query commands: Join and Union are SQL terms (Union also implies deduplication, which Append does not do), and Concatenate is a text function (Text.Combine / & operator) for joining string values, not tables.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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Join
Why it's wrong here
In Power Query, 'Join' is not a transformation name; the equivalent operation is implemented as 'Merge Queries'. While merge operations internally use join kinds such as Left Outer, Inner, and Full Outer, referring to the action as 'Join' is ambiguous and does not correspond to a specific Power Query command. A user looking for 'Join' in the ribbon or in the Power Query editor would not find it, which is why this option is incorrect.
- ✗
Concatenate
Why it's wrong here
Concatenate in Power Query is a text function (or a transformation like Combine Columns) that joins string values, not tables. Combining tables requires row-level operations (Append) or column-level key-based operations (Merge). Using Concatenate on tables would produce a textual representation of the table objects, not a structurally valid combined table, so it does not satisfy the requirement of combining multiple tables in the data model.
- ✓
Merge
Why this is correct
Merge is the correct Power Query transformation for combining tables horizontally. It matches rows between two tables based on one or more key columns, using a join kind such as Left Outer, Inner, or Full Outer. After merging, you expand the resulting nested column to bring in the desired fields from the second table. This aligns with the standard relational concept of a join, but within Power Query the precise name is 'Merge Queries'.
- ✗
Union
Why it's wrong here
"Union" is not a specific named transformation or method available directly within Power Query for combining tables. While the conceptual operation of vertically stacking rows from multiple tables is a common data manipulation task, Power Query implements this functionality through the "Append Queries" feature. This option is tempting because the term "union" is widely recognised in SQL and other data contexts for combining datasets with compatible structures by adding rows. However, to achieve this in Power Query, one would utilise "Append Queries" to stack tables, not a "Union" function.
- ✓
Append
Why this is correct
Append is the correct Power Query transformation for combining tables vertically. It stacks rows from two or more tables that have compatible column structures, essentially performing a UNION ALL operation. The 'Append Queries' command and its variant 'Append Queries as New' allow you to add rows from one table to another. When column names differ, you can map them explicitly, and unmatched columns are filled with null values.
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