>>You don't have to have N'ALTER TABLE
>>
>>and 'ALTER TABLE ...
>>will work exactly the same as the command is declared nvarchar. So, you may safely drop it in this particular case if you're only using 'English' letters.
>
>If I am using foreign characters, but still have the nvarchar declaration, will ALTER TABLE work as is or I will have to add the N in front?

In this case I suggest to keep N' in front.