NT-Logon name in MSSQL table


Would someone like to answer the following question?
I tried to get the NT-logon name saved into a table, but I
couldn't find the right function. I succeeded in getting the
Workstationname saved, by using the function sysuser, but
that's not what I would like to get.
Does anyone know how to get a NT-logon name (either
by a MSSQL function or by a Delphi function?)