What is the recommended way to design a database to deal with the following situation:

A school system has a central database. Data is entered at member schools either directly into the master DB or into detached copies of the master DB. If copies are used, they are to be synchronized periodically with the master DB.

What method do you recommend to avoid creating duplicate keys? I would prefer that keys are single fields but not GUIDs, because those are just too long.

What procedure needs to be followed to synchronize data?

TIA,

Lex