Checking Synchronization issue in SQL?
No, the Second Query won't Delete anything.

In the statement prior to the delete you change the oldID to the newID so there aren't any records with the oldID in that table.



Difference between the two Queries

The first Query, inserts new records into the table, then deletes the records with the oldID

The Second Query, updates all the records removing the oldID's and replacing it with the newID's, so instead of inserting and then deleting the old records, it updates the old records UniqueID column

These both do very different things.