Pleas always tell which program version you are using!
This “Because of the unique key constraint, the insert of (2,100,200) fails”.
Doesn't this constarint exist on target as soruce as well?
If the row exists on source it should also be possible to INSERT on target if the table CREATE statement is the same.
If the is a (server-side) CONSTRAINT on the data then of course it is not possible – but it is not a SQLyog issue then!
What am I missing?
We recently changed the order of operation for DATASYNC from INSERT -> DELETE -> UPDATE to DELETE -> INSERT -> UPDATE. That can be confusing (rows will be deleted and next inserted), but in the end data should come there.
Was it possible that you attach a small complete test case with a dump from the source as well as the target? Only one table with a few rows of data are required. I think that would the best way to secure that we do understand the problem.
You can create a ticket if you do not want to expose your data here. It can also be fake data as long as the issue is reproducable.
With FK's you should set Foreign Keys Check = 0. I repeat that the UK CONSTRAINT should not be an issue. If the row can exist on the source it should also insert on the target without problems.