Power Query Merge vs Append: Which Data Joining Method Do You Need?

Power Query merge and append are two distinct data-shaping operations built into Excel and Power BI. Merging joins separate tables side by side using matching column keys like a database, while appending stacks tables vertically by aligning matching column headers to make your dataset longer.

Key Takeaways

• Merge makes tables wider by combining data side by side using a shared key column.
• Append makes tables longer by stacking rows vertically on top of one another.
• Merging works similarly to a database join, allowing you to choose inner, outer, or left/right join types.
• Appending requires identical or closely matching column headers to stack data correctly.
• You can merge or append data from entirely different sources, such as combining a CSV export with a SQL database table.

If you have ever spent hours copying and pasting data from multiple sources into a single master sheet, you know the frustration of data preparation. In modern Microsoft 365 environments, tools like Excel and Power BI handle data integration natively through the Power Query engine. However, beginners often stumble when trying to bring multiple data sets together because they confuse the two primary combination tools available: merging and appending. Understanding the functional differences between these operations will save you hours of troubleshooting and keep your data models running efficiently.

Understanding Power Query Merge: Making Tables Wider

The merge operation in Power Query is designed to bring related information together side by side. Think of it as introducing two distinct tables that share a common piece of information—such as a customer ID, product code, or employee number—and linking them together.

When you initiate a merge, Power Query acts much like a relational database system. You select your primary table, choose a secondary table, and highlight the key columns that tie them together. Once matched, you can expand the secondary table to pull in only the specific columns you need, such as appending a customer name and email address onto a raw table of order transactions that only contained an ID number.

Choosing the Right Join Kind

Power Query offers several join types during a merge operation:

• Left Outer: Keeps all rows from the first table and matching rows from the second.
• Right Outer: Keeps all rows from the second table and matching rows from the first.
• Full Outer: Keeps all rows from both tables regardless of a match.
• Inner: Keeps only rows that find an exact match in both tables.
• Left Anti & Right Anti: Returns only rows that do not have a match in the opposing table.

Selecting the correct join kind ensures your final report does not accidentally drop crucial records or duplicate rows unexpectedly.

Mastering Power Query Append: Making Tables Longer

While merging focuses on width, appending focuses entirely on length. If you have data split across multiple files, months, or regional spreadsheets that share the exact same column structure, appending is the tool you need.

When you append tables, Power Query takes the rows from your first table and stacks the rows of the second table directly beneath them. The column headers must align properly for this to work smoothly. If your January sales export and your February sales export both contain columns for Date, Product, Quantity, and Revenue, an append operation will seamlessly combine them into a single comprehensive twelve-month history table.

Append vs. Folder Import

While you can manually append dozens of individual queries together, Power Query also offers a specialized folder connector. If you drop all your monthly reports into a single Windows or SharePoint folder, Power Query can combine and append all files automatically. This approach is much more scalable if your data sources grow month over month without manual intervention.

Combining Across Different Data Sources

One of the most powerful features of Power Query is its agnostic nature regarding data origins. Because the underlying engine abstracts the connection layer, you are never restricted to combining files of the same type.

You can easily merge a local Excel spreadsheet containing offline targets with a live SQL Server database tracking actual performance. Similarly, you can append CSV exports pulled from legacy systems with cloud data originating from SharePoint lists. As long as the structural requirements for a merge (a shared key) or an append (matching column headers) are met, the original location of the data does not matter.

Conclusion and Next Steps

Mastering the distinct behaviors of merging and appending is a foundational step in transforming your spreadsheet workflows from manual chores into automated processes. By letting Power Query handle the heavy lifting of joining and stacking data, you eliminate human error and free up hours of valuable time each month.

To dive deeper into how Power Query cleans, transforms, and automates your Microsoft 365 data workflows, Listen to the full episode of the podcast for an in-depth, jargon-free breakdown of applied steps, the M language, and beginner best practices.

Frequently Asked Questions

What is the main difference between merge and append in Power Query?

Merge makes your table wider by joining two tables side by side using a shared key column. Append makes your table longer by stacking the rows of multiple tables vertically based on matching column headers.

Can I merge tables that come from different file formats?

Yes. Power Query allows you to merge or append data from completely different sources, such as combining an Excel worksheet with a SQL database or a SharePoint list, as long as the relational or structural criteria are met.

What happens if my column names do not match when appending?

If column headers do not match during an append operation, Power Query will create separate columns for the unmatched headers, resulting in empty or null values for rows where those columns did not originally exist.

Do I need to know how to write code to use merge or append?

No coding is required. Both merge and append operations are fully accessible through friendly graphical buttons and dialog boxes within the Power Query editor in Excel and Power BI.