Answered

Adding a column to a data table

(0) Share

Report

Posted on by MW-24101252-0

Hi all,

In Power Automate Desktop I have a flow where a data table is created. Data for this table is extracted from a webpage, and the table ends up with Column A and Column B, each containing several rows.

Now, I need to add a third column (Column C) where I want to insert the same number for every row. The number is stored in one of my current flow variables. This number will be identical across all rows.

What is the best way to achieve this?

Categories:

Power Automate Desktop

I have the same question (0)

All responses (3)

Answers (1)

Verified answer

eetuRobo 4,484 Super User 2026 Season 1 on at

Like (1)

Report
Copy link

Link copied!
You can use "Insert column into data table" -action to create new column and then add the value to each row by using a loop and "Update data table item"

Or you could use .NET Script

This is how the Run .NET script looks like:

MyDataTable.Columns.Add("Column C", typeof(string)); foreach (DataRow row in MyDataTable.Rows) { row["Column C"] = MyConstant; }

Was this reply helpful? Yes No
MW-24101252-0 5 on at

Like (0)

Report
Copy link

Link copied!

Thank you @eetuRobo, I used the .Net-approach - and it works.

However, when I try to merge the datatable - with the now 3 columns - into another datatable, let's call it NEWdatatable also consisting of three columns, I now get the error "Warning: Deferred type provided and the data is not transferred to NEWdatatable, only the rows for each data line is created.

This was not the issue when I only had column A and B - . Do you have any idea to why that is?

Was this reply helpful? Yes No
Suggested answer

eetuRobo 4,484 Super User 2026 Season 1 on at

Like (0)

Report
Copy link

Link copied!

Good to hear it works.

About the merge issue I think its just a warning you get when using Power Fx enabled flow with dynamic variable. I've noticed that it gives very easily "Deferred type provided" -warning. Its not an error but a warning and so it doesn't really mean anything is broken or faulty in the flow.

https://learn.microsoft.com/en-us/power-automate/desktop-flows/power-fx

If you recreate the flow with Power Fx not enabled the warning should not appear at all.
If you want to use Power Fx then I would just do the regular For each loop so the first method I gave. That way you shouldn't get the warning and its easier to debug in the low-code actions than with the script. And since both methods are still doing a for each loop the same as long as you run the flow without the editor being open.

To the problem itself can you show screenshots of your flow and how the datatable looks after the merge? For me it works as expected even in the Power Fx enabled flow:
DataTableSecond which I will merge into DataTable

Now if you want to have the Column C to have the same value as you had before then either add another loop and update the value for all those rows that has empty value in the Column C. Or if its okay for to do the datatable merge before you add the new column then do that first so you only need to do the loop once when adding the new column with that default value.

Was this reply helpful? Yes No