How to do the equivalent of a JOIN query in Appwrite?

Hello,

I'm trying to get documents from a collection but I need to make sure that the document I pull is unique to another document in another collection. If it was sql, I would do a JOIN query but I don't know what's the equivalent in Appwrite. Thank you

There is no join in appwrite right now, you could do something like listDocuments where foreign_key = id to see if it exists already?