SESSION_USER
The SESSION_USER special register specifies the run-time authorization ID at the current server. The data type of the special register is VARCHAR(128).
The initial value of SESSION_USER for a new connection is the same as the value of the SYSTEM_USER special register.
The value can be changed by executing the SET SESSION AUTHORIZATION statement. For more information, see SET SESSION AUTHORIZATION.
Example
Select all notes from the IN_TRAY table that the user placed there himself.
SELECT * FROM IN_TRAY
WHERE SOURCE = SESSION_USER