Power Automate - How to get previous value of updated SharePoint List Item

#powerautomate #sharepoint #sharepointonline #powerfuldevs

Currently at time of writing, it is easy to kick-off a Power Automate flow when a SharePoint list item value changes and retrieve the new value.

However, to retrieve the previous value will require some work.

Below is the solution.

Overall Flow

Flow Breakdown

Flow Type: Automated cloud flow

Step 1 - Trigger when an item or a file is modified

Trigger Type: When an item or a file is modified

Step 2 - Get changes for an item or a file (properties only)

Purpose: To retrieve previous version number
Action Type: Get changes for an item or a file (properties only)

The Since value will be the Trigger Window Start Token

Step 3 - Send an HTTP request to SharePoint

Purpose: To retrieve all the versions of this particular updated list item
Action Type: Send an HTTP request to SharePoint

Uri: _api/web/lists/getByTitle('{Your_list_name}')/items(@{triggerOutputs()?{List Item ID from Step 1})/versions
Headers:
- Key: Accept
- Value: application/json; odata=nometadata

** It is important to add the Accept header to return JSON, else it will return as XML by default

Step 4 - Do a Test Run

Purpose: To get sample JSON which will be used for your next action.

After running, copy the JSON from the Outputs body section

Step 5 - Parse JSON response

Purpose: Turn the JSON response into objects which we can then use
Action Type: Parse JSON

Content: Body of the Send an HTTP request to SharePoint action
Schema:
- Click on Generate from sample
- Paste the JSON copied from Step 4 and click on Done button
- Once outside, click on 'Generate from sample' button to fill up the Schema field

Step 6 - Retrieve version of item

Purpose: Retrieve only the specific item version from the array
Action: Filter array

From: value from Parse JSON action
Where:
- VersionLabel from Parse JSON action
- Condition: is equal to
- Value: outputs('Get_changes_for_an_item_or_a_file_(properties_only)')?['body/SinceVersionLabel']. This value is from Step 2 - Get changes for an item or a file (properties only). There is no need to manually type this. Click on the Expression icon and choose the following in the popup window.

Step 7 - Retrieve value from the item version

Purpose: Retrieve value from old version and setting value to variable
Actions: Initialize Variable & Set variable (within Apply to Each control)

Here when setting the variable, you can select the column you want, in this case it was my Project field.

I then set the ProjectOldValue variable with the Project value.

Note that this flow can be modified as required for various scenarios, one being, if we need to retrieve the original value for an item (1st version), we can just hardcode the version value 1.0 for VersionLabel for Step 6.