Complete or Full Backup/Restore
BACKUP DATABASE [database_name]
TO DISK = 'path\backup_filename_full.bkp'
WITH INIT
RESTORE DATABASE [existing_database_name]
FROM DISK = 'path\backup_filename_full.bkp'
RESTORE DATABASE [new_database_name]
FROM DISK ='path\backup_filename_full.bkp'
WITH MOVE 'database_name TO 'path\new_database_name.mdf'
MOVE 'database_name_log' TO 'path\new_datanase_name.ldf'
Differential Backup/Restore
BACKUP DATABASE [database_name]
TO DISK ='path\backup_filename_diff.bkp'
WITH INIT, DIFFERENTIAL
As we know the Differential contains only the modified since last full backup, so we have to RESTORE the full backup first with NORECOVERY and then differential with RECOVERY statement.
RESTORE DATABASE [database_name]
FROM DISK 'path\backup_filename.bkp'
WITH NORECOVERY
RESTORE DATABASE [database_name]
FROM DISK 'path\backup_filename_diff.bkp'
WITH RECOVERY