SQL Server唯一的列集，不使用约束 - 按900字节限制获取位

I have a table which contains 3 nvarchar(255) columns and a combination of these 3 columns must be unique. Normally I would create a Unique constraint, but in this case, I am hitting the 900 byte limit. Since I have to support SQL Server 2000, I can not use Include columns to get around this situation.I have a table which contains 3 nvarchar(255) c