guys..

I need some help on a query.
I need to query how many hours one student logged on perday.for exapmle the login time for 202050 is 15:53:48 and logout time is 15:58:19

Studentno logintime
----------- ----------
202050 21-MAY-2002 15:53:48
202050 21-MAY-2002 15:53:46
202050 21-MAY-2002 15:54:50
202050 21-MAY-2002 15:55:52
202050 21-MAY-2002 15:56:54
202050 21-MAY-2002 15:57:56
202050 21-MAY-2002 15:58:19

202051 22-MAY-2002 11:53:48
202051 22-MAY-2002 12:53:46
202051 22-MAY-2002 12:54:50
202051 22-MAY-2002 15:55:52

202051 23-MAY-2002 15:56:54
202051 23-MAY-2002 15:57:56
202051 23-MAY-2002 15:58:19

any help is much appreciated!!!