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When using PowerQuery and getting ‘Files from a folder’, there is a risk that your query will break if the files in the folder do not start with exactly the same file name as when you first created the PowerQuery (especially if you want to keep the column Source.Name). This happens when your query tries to ‘Use First Row as Headers’ but the file name has changed. Below an easy fix for promoting headers when name can change.
Name of top file changes in folder
The issue relates to how Windows stores the files in a folder and having the order change e.g. August is placed in a folder but now it appears ahead of January.
As shown below in the PowerQuery window, at this point in the Query, when we promoted the headers, the header name became the name of the first file it saw in the folder i.e. CDE.xls .
promoting headers when name can change
This would be fine if we always knew that the file CDE would be in the folder and no other file will ever be sorted above it, so you will not be able to put the file ABC into the folder as it will automatically go to the top of the folder and break the PowerQuery.
So below, when ABC is now in the folder, the PowerQuery breaks because at this point it is looking for a column name called CDE but the column is now called ABC.
promoting headers when name can change
Create your own Source Name column and delete the original
The easiest way to address this, without complex M formula, is to create a new Custom Column that pulls through the source names you want to keep, but on the rows that contain the headers, you want to change the source file name to something generic, like Source Name!
In plain English we are going to tell PowerQuery to look at another column where we know the Header names won’t change (in the example below, column 2 will always have the words StoreName in the row which we want to use as headers). In those rows it will write the words “Source Name” but everywhere else it will pull whatever is in the original Source.Name.
You could use the Conditional Column tool as shown below or just write the IF formula.
promoting headers when name can change
The end result will look like this. The old Source.Name doesn’t change, but note that the new Source Name, on the row that we will eventually use as the headers, now has the words “Source Name” which will always appear there no matter which file is the first file in the folder.
promoting headers when name can change
Delete the original Source.Name column (it has done its job but will cause issues further down the line) and use the new Source Name column going forward.
Fix up the next steps to rather use the new column and your PowerQuery should now be immune to changes in file names and the resultant risk of sort order issues!
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