Unable to retain attachments while performing 'Join' between two feature classes.

[JamesVarghese_DUC]

I assume it might be very common to download data with attachments from ArcGIS Field Maps and perform a 'Join' operation with another feature class in ArcGIS Pro or ArcMap. So here is what I'm attempting to do: I have two feature classes that have associated attribute tables and I'm trying to perform a 'Join' in ArcGIS Pro 3.0.0. One of the feature classes was downloaded from ArcGIS Field Maps that contain attachments (field photos). I used the following article to download the feature class from Field Maps How To: Download attachments from a hosted feature service (esri.com)
As a stand-alone feature class, I can open the attachments and view the photos just fine. The other feature class has no attachments and contains only attributes.

I have tried several times to 'Join' ('Add Join', 'Join Field', 'Spatial Join' etc.) the two feature classes but in all cases the attachments/photos are NOT included in the Joined feature class/attribute table. I'm aware of the 'Maintain Attachments' Maintain Attachments (Environment setting)—ArcMap | Documentation (arcgis.com) option but this functionality is absent in the 'Join' Geoprocessing Tool. Is there a work around or an easy way to include the attachments while performing the 'Join' operation or am I missing something?

Following are the files that I'm working with:

Feature Class 1: Field_Sites (Created in ArcGIS Pro that has a bunch of attribute column information including a common field that has site numbers that are also present in Feature Class 2)

Feature Class 2: Field_Maps_Sites
                             Field_Maps_Sites_ATTACH
                             Field_Maps_Sites_ATTACHREL

Feature Class 2 was downloaded from ArcGIS Field Maps that contain attachments and relational table.

[RhettZufelt]

So, you are joining Feature Class 1 to Feature Class 2, not the other way?

If so, you should see the attachement(s) in the attributes pane when you select a feature in FC 2.  However, it seems you have to re-configure the popup for FC 2 if you want the attachment to show there (they don't automatically show as they do with initial FC).

R_

[JamesVarghese_DUC]

Apologies for not clarifying the question. Lot of details to be mentioned.

I did not know that the order in which the Join is performed, matters. I was initially trying to Join 'Feature Class 2' (with attachments) to 'Feature Class 1' (without attachments). The resulting join on Feature Class 1 has all the attributes from Feature Class 2, however without attachments. It seems the attachments are not getting transferred after the Join when done in this order. Wondering if it has anything to do with the BLOB field of the attachments. I also tried 'Enabling Attachments' via the Geoprocessing tool on Feature Class 1 before performing the 'Join' but was unsuccessful in transferring the attachments. I did not find any 'List of Attachments' to be configured in the Pop-up after the Join was performed.

Now, regarding the Join performed the other way around. Thanks for suggesting the idea. I just now tried to perform a permanent join (Join Field) by joining 'Feature Class 1' (without attachments) to 'Feature Class 2' (with attachments) and it is working successfully, and the attachments are retained, although it does not work with a temporary join such as 'Add Join'. This is a temporary solution for my problem so I will work with this for now.

Ideally, I was trying to join Feature Class 2 to Feature Class 1 followed by a third feature Class (Feature Class 3) with attachments, but the third feature type is a point and not a polygon. Following are the geometry types of the feature classes:

Polygon Feature Class 1 (without attachments)
Polygon Feature Class 2 (with attachments)
Point Feature Class 3 (with attachments)

All the three above mentioned files are within the same Geodatabase. The three Feature Classes have a common field called 'Site Number' and based on it I was hoping to transfer attachments (field photos) from Feature Class 2 and Feature Class 3 To Feature Class 1 using Join or any other tool in ArcGIS Pro. Any advice is welcome on how to go about doing this task. If it helps, Feature Class 2 and 3 were used to take pictures in the field using the ArcGIS Field Maps App.