SQL server keeps log for every transation.So you can recover your modified data from the log as well without backup.
Here is the sample source code.
Select [PAGE ID],[Slot ID],[AllocUnitId],[Transaction ID] ,[RowLog Contents 0]
, [RowLog Contents 1],[RowLog Contents 3],[RowLog Contents 4] ,[Log Record]
FROM sys.fn_dblog(NULL, NULL)
WHERE AllocUnitId IN
(Select [Allocation_unit_id] from sys.allocation_units allocunits
INNER JOIN sys.partitions partitions ON (allocunits.type IN (1, 3)
AND partitions.hobt_id = allocunits.container_id) OR (allocunits.type = 2 AND partitions.partition_id = allocunits.container_id)
Where object_id=object_ID('' + 'dbo.student' + ''))
AND Operation in ('LOP_MODIFY_ROW','LOP_MODIFY_COLUMNS')
And [Context] IN ('LCX_HEAP','LCX_CLUSTERED')
Here is the artcile, that explains step by step, how to do it.