How can I merge two libaries into one?

[yvev]

If the tags are in the files, it doesn't matter what MusicBee exports. Check some of the files with the tag inspector to see what's actually there. If the tags are missing, go back to your other library and confirm how they're being saved.

The reason I need to merge the two libraries directly is that the files of the two libraries are stored in other computers, and I cannot update the new library after merging. If I can scan and update, all the tags can come back again. But I cannot update. I thought that the information of all tags could be obtained by exporting  to an xml file, but it did not.

[frankz]

The xml file export of the database exports what's in the library (play stats, when the file was added, playlists, "save to database" tags, etc). It does not contain data that's in your files because that data is already accessible to MB within the file itself.

It seems you want to use MB for some purpose other than what's intended (managing a library of media files that the program has access to).  MusicBee doesn't store most info that's already in the file in the database as that would be redundant. You're going to have problems doing what you want to do with this program because it's not meant to do it.  You're probably better off exporting tags from each set of files (somehow) and managing the list in a spreadsheet or database program.

[yvev]

OK.
Thanks for any help.