>>>In the book I use (SQL 2005 Unleashed) the author is using the following naming convention for UNIQUE constraint:
>>>AK_TABLENAME_FIELDNAME
>>>
>>>Do you think AK stands for Alternative Key? Or what else could it be?
>>>
>>>Also, how important and where do you use the names of constraints (other than when you create them)?
>>
>>If you need to drop a constraint, you need a name.
>
>I understand. But it is not used anywhere in my code, right? That is, if a constrained stops the update does the error message contain the constraint name? (if so, the user will see it and there it is important).

As far as I remember, the constraint name is not shown in the error messages. Though, it is easy to test - just try inserting bad data.