Merge several PP4.8.6 boards into one only
Currently I am using several PP4.8.6 installations. Each one has its own internal registration system (always photopost).
I am planning now to merge some of them into one "master" only to get higher traffic for new images.
Categories in all different installations are always the same. Usergroups too. Normally, these are different users, but I do not know for sure whether some users might be registered in two different boards at the same time. Every Installation is using different prefixes in the database.
How can I do this without loosing the images, comments and userdata of each board. All shall be transferred to this one "master"?
Thanks in advance