Using Group by to Concatenate Text in Power Query

Most users know the Group By functionality in Power Query. It allows you to summarize data and aggregate the grouped values. The standard aggregations are Average, Median, Min, Max, Count Rows, Count Distinct Rows and All Rows. Most of these are aimed at numbers. Yet Power Query can also perform operations relevant to text.

In this post you learn how to group your data and concatenate text values. With the right function, you can concatenate strings into a single cell using the group by functionality. The effect is similar to using CONCATENATEX in DAX. So how can you use group by to concatenate grouped text values?

1. The dataset

Imagine below data set. You summarize the rows so that only a single row is available for each product. On top of that you sum the grouped sales values. Both operations can be done using the user interface. The challenge is to concatenate the grouped text values of the sellers into a single column. You will write some custom code to solve this. Let’s get going!

Data set for grouping

To summarize the data Product and then Sum the underlying sales you can:

  • Go to the Home Tab -> Click Group By
Using the Group By functionality

In the Pop-up screen:

  • Click Advanced
  • Group By -> Product
  • In the aggregation section, add a new column name called ‘Sales’, set the operation to Sum and select Column ‘Sales’.

So far everything can be done by the user interface. The challenge left is to create that combines all seller names in a comma separated list. The user interface does not provide the right code. Yet it does provide a template that shows how to use an aggregation function within the Table.Group function. Let’s go ahead and add a ‘dummy’ aggregation that prepares the code for the next step. What you can do is:

  • Click on Add aggregation, name the column Sellers, use the Sum Operation on the Seller column. Click OK.
Group By menu to specify aggregations

The operation groups the data by Product, and sums the underlying sales. Notice that the Seller column contains an error. This error occurs since we told Power Query to perform a Sum operation on text values. Clearly, the Sum operation only works on numbers and won’t concatenate text values.

Error message when summing text values

Yet for our purposes, this setup is great. We can now correct the wrong formula without having to write everything from scratch.

2. How does Table.Group work?

Before we can change the code, it is good to have a look at how Power Query groups data. When grouping data, Power Query uses the Table.Group formula.

The Table.Group formula takes three variables. It needs:

  1. a table. In this case the step #”Changed Type” refers to a table.
  2. the key columns. These columns specify the columns to group the data by. In this case the column named “Product” is the key to group the data by.
  3. aggregated columns as list. The formula’s that are used to aggregate the data should be able to handle a list. The underlying data is always provided as a list for aggregations. In the example the formula List.Sum is used to sum the sales numbers.

Focus on step 3 for a moment as this argument provides a crucial hint for what formulas you can use to summarize text values. The aggregation formula needs to be able to handle a list as variable. When searching the Power Query formula reference you may stumble upon the Text.Combine function.

The Text.Combine function combines text and takes a list as input. The formula then returns a text value that is the result of joining all underlying text values. And each value that is concatenated, can be separated using a separator.

As input arguments, the formula requires text to concatenate (as a list) and it needs to know with what separator to use. This is exactly what we need for our challenge.

3. Concatenate Text Values

3.1. Table.Group with Text.Combine

You now know which function to use to concatenate text values in Power Query. It is time to adjust the M-code generated by the user interface. We can try to incorporate the Text.Combine function in the formula containing the error. The part of the formula returning an error is:

{"Seller", each List.Sum( [Seller] ), type text}

To have it use the Text.Combine function you can change it to:

{"Seller", each Text.Combine( [Seller] , ", "), type text}

The first argument indicates which column (received as a list) provides the text to combine. In this case the column ‘[Seller]’. The second argument tells us what separator to add between the text. The example contains a comma and a space (“, “). After pressing Enter, below screenshot is the result!

text.combine function to aggregate text values

The names of the Sellers are now all within the same cell, and don’t return an error anymore. Goal reached! You have successfully combined the group by operation with the text.combine function.

3.2. All Rows and Extract Values

Another way to use group by to concatenate rows is by using the All Rows functionality. Imagine we again group the data by Product. You take the sum of the Sales column, but this time you also select the All Rows operation.

The result of the All Rows operation is a Table object containing all grouped records, you can see it below in the column Details.

When working with tables, you can retrieve the value from a column by referencing it between square brackets. A custom column with the formula = [Sales] results in the corresponding value within that column.

Yet when you reference a column in a different table or an earlier step in your query, a column reference results in a list containing all values from that column.

To learn more about the syntax of lists and learn from examples make sure to check out:
Lists in Power Query M / List Functions (200+ Examples).

Knowing this we can cook up a formula to reference all seller values in the table object of the Details column. To retrieve the Seller names the formula first references the Details column that contains the table object. And on top of that reference you reference the Sellers column within the table object. You can do that by writing:

= [Details][Seller]

On the bottom-left you can preview the grouped sellers found within the list item. The last step is to extract the values from this column. To do that:

  • In the Custom column, select the outward facing arrows and select Extract Values.
  • Choose for a Custom delimiter and write “, ” (without parenthesis) , then press OK.

The resulting formula looks very similar to what we wrote earlier:

= Table.TransformColumns(
     #"Added Custom", 
     {"Custom", 
         each Text.Combine(List.Transform(_, Text.From), ", "), 
         type text })

The only difference is that this formula includes the List.Transform and Text.From function. This addition is relevant for value types that are different than text.

If list functions like these are new to you make sure to check out this complete guide to lists in Power Query.

It took some slight adjustment of the M-Code but nothing you can’t handle. You willll get more comfortable with making manual changes the more you do it. To take a closer look, you can download the example file:

In this post you have learned that when you group data only aggregations are possible with functions that allow lists as input. Knowing this, you can leverage functions that take a list as argument, when grouping your data. I hope this post opens your mind for more experimentation. If you have any questions, or stumble upon useful formulas to leverage when grouping, I’d love to hear about them in the comments.

Enjoy Power Query!

About Rick de Groot

Rick is the founder and editor of BI Gorilla. He believes learning is one of the great pleasures in life and wants to share his knowledge to help you improve your skills.

Learn more about him here, connect with him on Twitter, Facebook and LinkedIn and subscribe to his YouTube Channel.

34 thoughts on “Using Group by to Concatenate Text in Power Query”

  1. Hi Rick,

    I was wondering if this little trick could also work inside the Table.AggregateTableColumn
    function. In principle it worked, however I failed in adding the separator argument, since the aggregations seem to either work differently or pass the arguments in a slightly different way?
    Do you have any idea?

    This works:
    Table.AggregateTableColumn(#”Merged Queries”, “My_Lookup_Table”, {{“Packagecode”, Text.Combine, “Combined Packagecodescodes”}})

    This doesn’t (also adding the ‘each’ statement doesn’t work):
    Table.AggregateTableColumn(#”Merged Queries”, “My_Lookup_Table”, {{“Packagecode”, Text.Combine([Packagecode], “, “), “Combined Packagecodescodes”}})

    Reply
    • Hi Marc,

      That’s an interesting challenge. I didn’t try this before you asked. So your code is working like:

      Table.AggregateTableColumn(#”Merged Queries”, “My_Lookup_Table”, {{“Packagecode”, Text.Combine, “Combined Packagecodescodes”}})

      To make it working with a seperator you can do:

      Table.AggregateTableColumn(#”Merged Queries”, “My_Lookup_Table”, {{“Packagecode”, each Text.Combine( _ ", " ), “Combined Packagecodescodes”}})

      You were on the right path using the each keyword. You can then reference the “_” (underscore), to indicate it’s for each value within that column, and then add the separator as argument.

      Hope that helps and thanks for asking your question.

      Best regards,
      Rick

      Reply
      • Hi Rick,

        that was the missing link! Thank you so much, it works as expected and saved me quite some workarounds… AWESOME! Thanks 🙂

        kind regards,
        Marc

        Reply
  2. Thanks! Now can you help doing the same with a date column? I know somewhere you need to do a Date.ToText but it’s not working.

    Reply
    • Hi H,

      Great question, that’s a little more difficult. What you can do is:


      {“Seller”, each Text.Combine( List.Transform( _ , (DateList) => Date.ToText( DateList ) ) , ", " ), type text }

      The part with List.Transform is added, so that Power Query can first transform each Date that needs to be grouped. Only to then combine them together.

      Hope this helps!
      Rick

      Reply
  3. Great! This helped me a lot.!
    What about if you just want to group and take the values for the latest one. Let me explain:
    In the example, let say you just want to now the values where the date is the oldest. Then you should have:
    19/04/2018 | Face Cream | Jaime | 90.07
    22/04/2018 | Hand Soap | Lisa | 74.05
    ..etc

    Reply
  4. Thanks Rick, this helpled me a lot! A quick question: is there a quick way to remove potential duplicate values in the newly created column? Many thanks!

    Reply
    • Hi Anne-Sophie,

      That’s a great question. This is the answer I gave to someone else in the comments:

      To get a list of UNIQUE seller names, you can add List.Distinct to the formula.

      The original formula for grouping in my example file is:

      = Table.Group(#”Changed Type”, {“Product”}, {{“Sales”, each List.Sum([Sales]), type number}, {“Sellers”, each Text.Combine([Seller], ” , “), type text}})

      You can change this to the following to get a unique list of names

      = Table.Group(#”Changed Type”, {“Product”}, {{“Sales”, each List.Sum([Sales]), type number}, {“Sellers”, each Text.Combine(List.Distinct([Seller]), ” , “), type text}})

      Hope that helps!

      Reply
  5. Can i accomplish this same csv text column result using #”Aggregate . . . ” given it in a left join scenario to produce the one left side hit for many right side hit results using #”Group By . . . ” requires defining every left side table column value you want included in the output results? I’ve outlined the scenario for this in more detail in this post https://stackoverflow.com/questions/64674141/how-to-enable-left-join-with-mysql-group-concat-csv-merged-instances-of-right-si .

    Reply
  6. This is a great article, thank you so much for posting it! One other question, how do you update the new tables if new information is added to the original worksheet Source. I tried clicking on the ‘Refresh All’ in the Data Tab, but it didn’t add the new row of information from the Source Worksheet. Thank you!

    Reply
    • Hi Stephanie,

      A ‘Refresh All’ should normally do the trick. In what form is your source data? Is it in a table and does Power Query pick up the table? If it’s not in a table, it could be that Power Query picks up the named range. Then if this named range is not including the additional data, it won’t be picked up.

      Best regards,
      Rick

      Reply
    • Hi Rachel.

      The grouping is required. But what you could do to keep all your columns, is to specify an additional column in the grouping screen. And in this extra column, select the operation : All Rows. After grouping, you will then see an additional column containing all the columns that were grouped earlier.

      Reply
  7. Hi
    Just wanted to say this is the first article I read on this website and I can tell it has some really good content with great examples.
    On a side note: just bookmarked this site right next to Stackoverflow.

    Reply
  8. Nice tip!!

    but how to make it a unique SELLER NAMES for eg!

    Sun Lotion 2951.06 Richard,Lisa,Dennis,Mark,Mark,James,James,James

    Req Result:

    Sun Lotion 2951.06 Richard,Lisa,Dennis,Mark,James

    Reply
    • Hi Muhammed. That’s a great question! To get a list of UNIQUE seller names, you can add List.Distinct to the formula.

      The original formula for grouping in my example file is:

      = Table.Group(#”Changed Type”, {“Product”}, {{“Sales”, each List.Sum([Sales]), type number}, {“Sellers”, each Text.Combine([Seller], ” , “), type text}})

      You can change this to the following to get a unique list of names

      = Table.Group(#”Changed Type”, {“Product”}, {{“Sales”, each List.Sum([Sales]), type number}, {“Sellers”, each Text.Combine(List.Distinct([Seller]), ” , “), type text}})

      Reply

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