One of the things that I’ve complained about in the past is that there is no built in way for Power Query to be able to pull up the path for the current workbook.  Today I’m going to show you how I solved that problem by building a parameter table for Power Query in Excel, then link it into my queries.

Quick Note!  WordPress is determined to drive me crazy and is replacing all of my straight quotes (SHIFT + ‘) with curly quotes.  Since curly quotes are different characters, they will cause issues if you copy/paste the code directly.  I’ll get this sorted out, but in the mean time, just make sure you replace all “curly quote” characters with straight quotes.

To do this successfully, we need to pieces; an Excel table, and a Power Query function.  So let’s get to it.

Building a Parameter Table

The table is quite simple, really.  It’s a proper Excel Table, and it has a header row with the following two columns:

• Parameter
• Value

Once created, I also make sure that I go to the Table Tools tab, and rename the table to “Parameters”.

Pretty bare bones, but as you’ll see, this becomes very useful.

Now we add something to the table that we might need.  Since I’ve mentioned it, let’s work out the file path:

• A8:     File Path
• B8:     =LEFT(CELL(“filename”,B6),FIND(“[“,CELL(“filename”,B6),1)-1)

Now, as you can see, column A essentially gives us a “friendly name” for our parameter, where the value ends up in the second column:

While we’re here, let’s add another parameter that we might have use for.  Maybe I want to base my power query reports off the data for the current day.  Let’s inject that as well:

• A9:     Start Date
• B9:     =TODAY()

Good stuff.  We’ve now got a table with a couple of useful parameters that we might want when we’re building a query.

Adding the Parameter Function

Next, we’re going to add the function that we can reference later.  To do that:

• Go to Power Query –> From Other Sources –> Blank Query
• Go to View –> Advanced Editor
• Replace all the code with the following:

(ParameterName as text) =>
let
ParamSource = Excel.CurrentWorkbook(){[Name=”Parameters”]}[Content],
ParamRow = Table.SelectRows(ParamSource, each ([Parameter] = ParameterName)),
Value=
if Table.IsEmpty(ParamRow)=true
then null
else Record.Field(ParamRow{0},”Value”)
in
Value

• Click Done
• Rename the function to “fnGetParameter”
• Go to Home –> Close & Load To…
• Choose to create the connection only, avoiding loading to a table or the Data Model

And just in case you think this means it didn’t work, we expect to see that it didn’t load in the queries window:

Making Use of the Parameter Table

Okay, so now that we have this in place, how do we go about using it?

Let’s create a ridiculously simple table:

Now, click in the table and go to Power Query –> From Table.

We’ll be taken into the Power Query window and will be looking at our very simple data.  Let’s pull the contents of my parameters into columns:

• Go to Add Column –> Add Custom Column
• Change the title to “File Path”
• Enter the following formula: =fnGetParameter(“File Path”)

Check it out!

Do you see that?  This is the path to the folder that holds the workbook on my system.  The formula we used in the table retrieves that, and I can pass it in to Power Query, then reference it as needed!

How about we do the same for our date?

• Go to Add Column –> Add Custom Column
• Change the title to “First date”
• Enter the following formula: =fnGetParameter(“Start Date”)

The key here is to make sure that the value passed to the parameter function is spelled (and cased) the same as the entry in the first column of the parameter table.  I.e. You could use “FilePath”, “File Path”, “Folder”, “My File Path” or whatever, so long as that’s the name you gave it in the first column of the Parameters Excel table.

And what happens if you pass an invalid value?  Say you ask for fnGetParameter(“Moldy Cheese”) and it’s not in the table?  Simple, you’ll get null returned instead. 

Implications of Building a Parameter Table for Power Query

The implications for this technique are huge.  Consider this scenario… you create your workbook, and store it in a folder.  But within that folder you have a subfolder called “Data”.  Your intention is to store all of your csv files in that folder.  And, for argument’s sake, let’s say that it’s a mapped drive, with the path to your solution being “H:\My Solution\”

No problem, you build it all up, and it’s working great.  You keep dropping your text files in the data folder, and you can consolidate them with some M code like this:

let
Source = Folder.Files(“H:\My Solution\Data”),
#”Combined Binaries” = Binary.Combine(Source[Content]),
#”Imported CSV” = Csv.Document(#”Combined Binaries”,null,”,”,null,1252),
#”First Row as Header” = Table.PromoteHeaders(#”Imported CSV”)
in
#”First Row as Header”

Things run along for ages, and that’s awesome, but then you need to go on vacation.  No worries, it’s Power Query and easy to use, you can just get your co-worker to update it… except… on your co-worker’s machine that same drive is mapped not to the H:\ drive, but the F:\ drive.  Doh!

We could recode the path, but what a pain.  So how about we use the parameter table to make this more robust so that we don’t have to?  All we need to do is modify the first couple of lines of the query.  We’ll pull in a variable to retrieve the file path from our parameter table, then stuff that into the file path, like this:

let
SolutionPath = fnGetParameter(“File Path”),
    Source = Folder.Files(SolutionPath & “Data”),
#”Combined Binaries” = Binary.Combine(Source[Content]),
#”Imported CSV” = Csv.Document(#”Combined Binaries”,null,”,”,null,1252),
#”First Row as Header” = Table.PromoteHeaders(#”Imported CSV”)
in
#”First Row as Header”

How awesome is that?  Even better, the SolutionPath shows as a step in the Applied Steps section.  That means you can select it and make sure the value is showing up as you’d expect!

Practical Use Case

Several months back I built a solution for a client where we stored his Power Query solution in a folder, and we had data folders that were created on a bi-weekly basis.  Each of those folders were named based on the pay period end data (in ISO’s yyyy-mm-dd format), and were stored in a path relative to the master solution.

Naturally, I needed a way to make the queries dynamic to the master folder path, as I did the development in my home office, then emailed the updated solution files to him in his New York office.  He had different drive mappings than I do, and his team had different drive mappings than he did.  With half a dozen Power Queries in the solution, having them manually update the code each time a new user wanted to work with the file just wasn’t an option.

This technique became invaluable for making the solution portable.  In addition, by having a formula to generate the correct end date, we could also pull the data files from the right place as well.

I still want a Power Query CurrentWorkbook.FilePath method in M, but even if I get it this technique is still super useful, as there will always be some dynamic parameter I need to send up to Power Query.

I hope you find this as useful as I have.

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