With Halloween around the corner what better topic to discuss than phantom reads. A phantom read occurs when rows have been inserted after a read operation and becomes visible in a follow-up read operation within the same transaction.
I will show you what this looks like with an example. Please note the code will not work for you because I dropped the foreign key constraint within the person.person table just so I could show you the example.
Arun mentions that the serializable isolation level prevents phantom reads. So do the repeatable read and snapshot isolation levels.