Power Query: How to Combine files based on a list

Power Query has a really powerful feature that lets us combine all the files in a folder. However, sometimes the files are not contained in a single folder. Sometimes they are spread out in multiple places. How can we deal with that? That’s what we are looking at in this post: how to combine files based on a list.

Table of Contents

• Source Data Table
• Connect to and transform a single workbook
• Reuse the transformation steps
• Expand the data to combine files
• Making additional transformations later
• Conclusion

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Source Data Table

First, let’s start by making a Table of all the files to combine, including the sheets or tables in those workbooks we want to use.

In this example, I will use worksheets, but you could use Tables or named ranges.

You will notice the worksheets in each workbook have different names; this is often a tricky Power Query situation, but this is no problem for this method.

Load the Table, which for the example is called SourceFiles, into Power Query.

Connect to and transform a single workbook

We now need to get the code to connect to each workbook. I’m assuming you’re not an M-code expert, so we will work through this without writing any code.

In Power Query, right-click on the Queries pane and click New Queries > From File > From Workbook.

If your file is a different file type, use the relevant connector for that file.

Navigate to one of the files in the list and click Import.

In the Navigator window, select the relevant source data, then click OK.

Next, we need to make any necessary transformations for that single workbook.

For the example:

• Removed the top 4 rows
• Promoted the headers
• Changed the data type
• Filtered to exclude null values from the Account Code column

Here is the final table for a single workbook of the example data.

Reuse the transformation steps

In the single workbook query, click View > Advanced Editor.

Copy all the code, then click Done to close the window.

Go back to the query which lists all the files.

Click Add Column > Custom Column

In the Custom Column dialog box, give the column a name (I’ve used Data) and paste the code we copied earlier into the Custom Column formula box.

We just need to make a few small adjustments to the code.

• Where the file path is hardcoded, change it for the column name containing the file path.
• Where the sheet name is hard coded, change it for the column name containing the sheet name.

For our example. The code changes from this:

Source = Excel.Workbook(File.Contents("C:\Examples\Data\2022\P12\P12 2022 Trial Balance.xlsx"), null, true),
Dec_Sheet = Source{[Item="Dec",Kind="Sheet"]}[Data],[insert code]

To this:

Source = Excel.Workbook(File.Contents([File Path]), null, true),
Dec_Sheet = Source{[Item=[Sheet Name],Kind="Sheet"]}[Data],

Click OK to close the Custom Column dialog box.

The Power Query preview window now looks like this:

Expand the data to combine files

For the sake of simplicity, we will expand the columns using the Expand icon. If you could have new data at any point, you should expand the columns dynamically. There is a blog post about that method here: How to expand columns dynamically in Power Query

Click the expand icon. We don’t want the original column name as prefix, so uncheck that, then click OK.

BOOM!

That’s it. You’re done!

We can now delete the single workbook query, as it serves no purpose.

If we add more rows to the SourceFiles Table, the query will incorporate those files too.

Making additional transformations later

At some point, the source data may change, and you may want to change the query. So, what can we do?

• Create a new blank query – right-click on the Queries pane, click New Query > Other Sources > Blank Query.
• Copy and paste the code from the Custom column step into the new query.
• Change the [File Path] and [Sheet Name] columns back to hard-coded values which reference a specific file.
• This changes the new query back to a standard query.
• Make any amendments you wish to that query.
• Finally, Copy and paste the code back into the Custom Column.

Conclusion

We’ve seen that we can easily combine all the files in a list using Power Query. It takes a few minor amendments to the automatically generated code, but nothing we can’t handle. Now, it doesn’t matter where the files are, or what the sheets are called; we can easily combine them into a single data source.

Related Posts:

• Get data from folder in Power Query: combine files quickly
• How to use Power Query Custom Functions
• How to get data into Power Query – 5 common data sources

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