SQL Server 2008 R2 Restore a back up to a new database
You cannot access the records in a database backup without restoring it to a database. You can however restore it to a different database from the one that it was backed up from.

The following link illustrates how to do this using Transact-SQL: http://msdn.microsoft.com/en-us/library/ms190447(v=sql.105).aspx

and in Management studio: http://msdn.microsoft.com/en-us/library/ms177429(v=sql.105).aspx

Then once you have the new database you can write SQL to join the two instances (obviously security considerations will need to be taken into account first). E.g

SELECT Table1.*, Table1_Backup.* FROM Table1 
INNER JOIN DB_Restore.dbo.Table1 AS Table1_Backup ON Table1.ID = Table1_Backup.ID


or similar.

As @Flem mentions you could then use the MERGE statement to merge the two datasets, however you want.