I'm noticing something different when joining data onto feature classes in ArcGIS Pro (And Desktop) and I'm hoping someone will have insight. Here's my recollection of how joins work in ArcMap. When you join data from a foreign table onto a feature class, and that foreign data has a 1:M relationship with the feature class (a.k.a. multiple records in the foreign table with the same ID as a record in the feature class) then ArcMap will only return data from the first record in the foreign table. I actually did find a bullet about this in the Desktop 9.3 documentation (http://webhelp.esri.com/arcgisdesktop/9.3/index.cfm?TopicName=Add_Join_(Data_Management)). Yesterday I was joining data from one table onto a parcel feature class in Pro 1.1, and suddenly the feature class record count in the attribute table jumped by about 2,000. Pro gave me a warning that the table no longer had unique OID's due to the join. So did ESRI change how 1:M joins are handled somewhere along the way? It's happening in ArcMap 10.2.1 as well. All the data I'm joining is in a 10.2.1 file geodatabase. I don't see the bullet about only returning the first joined record anywhere in the Add Join tool's help for 10.2, so I'm wandering if that functionality was dropped. I know for some workflows that restriction on joins was an annoyance, but in my situation I wanted it cause for my analysis the parcel layer is the primary table and I don't want "Duplicates" popping up in it.
Thanks for any help you can provide,