So, I don't really want to rearrange the entire system to make this happen.

My current solution is simply to use 2 seperate queries. I SELECTed all of the relevant records from the memory-backed cacheDb_, and then in a single transaction, I am INSERTing them into the table in the disk-backed sessionDb_. I am assuming that this is slower than doing the whole thing in a single SQL command, but it is working for the moment.

However, I would still be interested in figuring out how to move data between two databases without having to do it one record at a time.