The two tables are intended to be part of the same "chat" partition (ie SQLite database). You can join them with a native SQLite query. Seems I should make this more clear.
I understand the two tables in your chat example, I think. I'm wondering how you get the rest of the user profile data (name, for example). Is that table in a totally different SQLite database? If so, can you join on that, or do you need to query it separately? Thanks!