I've got a Multiple Site Manager set up with 3 different sites. I'm wondering if it is possible to export all EE content/channels/data from one of the sites, and import that same site data into another Multiple Site Manager instance. Is this easily accomplished, or will it involve dark SQL magic?
In a word: no, nothing easy about this. All the data is stored in the same database tables using database-specific channels IDs, field IDs, entry IDs, etc, etc - which will almost for sure conflict with existing channels, fields, and entries in your destination database.
It's doable, but it's part-manual, part-automated, and requires a huge amount of analysis of both databases in order to figure out how you need to alter existing records so they don't conflict.