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 can use a hash function (although theoretically it doesn't guarantee that two different titles will have different hashes, but should be good enough: MD5 Collisions) and then apply the index on that column.

MD5 in SQL Server