There is no clean way to do it short of keeping a log of all changes "AND WHAT WAS DONE". Then combining the logs and processing them in sequential order and somehow having the log know what was done. What if someone updates information based on old data. Example: customer calls the sales guy and says "Add 10 more to my order" so the sales guy updates the order from 10 to 20. Later he wants to add another 10 but he can't reach the salesman so he calls the office and says, "Add another 10 to my order." So the office updates the order from 10 to 20 because they don't know about the 10 the salesman added. At this point the order should be 30 but the last edit was 20. Dates can have a similar problem. Even text fields if edited by two people would only result in the last edit if working solely by time. And that is only TWO users. What happens when a THIRD user updates the record. And user 3 updates the record between user 1 and user 2 but user 3 gets back to the office and updates his data first?
The only reliable solution is to log ALL RECORDS when changed when an edit is made then update the record. Then, when syncing, if the LOGGED record doesn't match the record you are updating a human being has to look at ALL LOGGED changes since to both records AND look at the original record and decide what to do.
How do I know this? I wrote a "simple" app for myself to store information across my multiple devices. No other users involved. What a mess!
