title: Unique identifier as primary key when syncing databases
body: <p>I have spent the best part of a day researching and testing different methods of syncing a SQL server database with CoreData on the Mac. I have tested both INT's and GUID's (sequential GUID's also) as my primary keys and although GUID's are by far the worst in terms of performance I can't see no other way of ensuring uniqueness across systems. </p>
  
  <p>Is using GUID's for primary keys the wrong way to go when syncing data between platforms? I find it hard to believe that companies use GUID's when syncing, but most articles I read on the subject seem to point to just that. If developers are using GUID's does anybody know how performance can be improved? I tried using a GUID as a primary key with a non clustered index and created a date field as my clustered index with no great performance improvement.</p>
  
  <p>Any help would be much appreciated, especially if you have tackled a similar problem. </p>