Você pode usar esta consulta:
select EnrollNo, convert(varchar, AttDateFirst, 8) as FirstTime,
convert(varchar, AttDateLast, 8) as LastTime,
convert(varchar, AttDateLast - AttDateFirst, 8) as [Time Diff]
from YourTable
para retornar os seguintes resultados:
EnrollNo FirstTime LastTime Time Diff
----------- ------------------------------ ------------------------------ ------------------------------
111 08:46:00 08:46:00 00:00:00
112 08:30:00 17:30:00 09:00:00
302 09:00:00 18:30:00 09:30:00
303 10:00:00 18:35:00 08:35:00
