Thanks, the same address could be in the log table twice in case they move out an address then after a year move back. so this is correct case.

we just don't want same address shows up for the students in two consecutive records.

The reason I join inserted and deleted is to want to make sure is to prevent some one update the table using the same data multiple times. so in this case inserted and deleted are the same.

then I use not exists to exclude for this case.

Does that sound correct?

Thanks