Gazareth (8/4/2015)That's really really easy then, probably the best case scenario. Merge the duplicate top levels based on whatever rules you have for this situation then delete the one with no children.
If both have children then follow this for each table in parent -> child order:
Starting at the top you can not merge the 'second' level to the other client because there is the constraint with the third level. So the second level can not be 'moved' if there is still a third level.
My presentation of the simplified problem was maybe not extensive enough. Sorry for that, but I thought that I was clear enough that each level has constraints to the tables above including the client entity ID and has constraints with the table below including the client entity ID. Sorry if that was not clear.
As said we have solved the problem, but is was not simple. Even the simplified version has a number of these caveats. And the real version has more. (For example that a merge action should be reversible.
Ben