Sql Server - Index on nvarchar field

Question

What is the good approach to keep a nvarchar field unique. I have a field which is storing URLs of MP3 files. The URL length can be anything from 10 characters to 4

Answer 1

You could create a hash code of the url and use this integer as a unique index on your db. Beware of converting all characters to lowercase first to ensure that all url are in the same format. Same url will generate equal hash code.