SQL Server 2008 - HashBytes computed column

Question

I\'m using SQL Server 2008.

I have a NVARCHAR(MAX) column called Title and i want to add an unique index for it. Because the column is bigger than 9

Answer 1

The hashbytes column gets created as a VARBINARY(MAX) unless you do specifically tell it that 20 bytes are plenty:

alter table dbo.Softs 
  add TitleHash AS CAST(hashbytes('SHA1', [Title]) AS VARBINARY(20)) PERSISTED

Once you've done that, then you can create your index (unique or not) on that column:

CREATE UNIQUE NONCLUSTERED INDEX [UIX_TitleHash] 
  ON [dbo].[Softs]([TitleHash] ASC)

Now this should work just fine.