So the question I have about Listing 6.28 is that I get that the uniqueness of the index is supposed to be guaranteed by the database/table. So my question is that in the example outlined by the author right under Listing 6.27 is fixed is by raising an exception during the save for request 2?
Basically does the database raise the exception for uniqueness now? And the model raises the exception sometimes as well? So when I code I must check when the user is created that it is valid, as well as when it is saved I need to check for exceptions?