Merging 2 layers, one with attachments and one without

[ClintonLunn]

Hi, I am trying to merge two layers. One with attachments hosted in AGOL, and the other which I published as a hosted feature layer from ArcMap and do not contain attachments. When I try to merge these layers on AGOL, the attachments do not end up in the resulting combined layer. How can I fix this? Thank you!Mer

[JayantaPoddar]

What happens if you enable attachments (although no attachments used) before publishing the feature service from ArcMap?

In case the issue still persist, check Merging together Attachment Data sets .

[CarmelConnolly]

Hi Clinton, 

I'm not sure this is possible within ArcGIS Online - I've managed to do this by downloading the layers and performing the analysis in ArcMap, this blog covers the work flow which might help: Working with Collector for ArcGIS without syncing to ArcGIS Online or Portal for ArcGIS. — Esri UK 

Carmel